Class 9 Maths Chapter 6 Exercise 6.2 Solutions covering area of triangles, trapeziums, rhombuses and Heron's Formula

Class 9 Maths Chapter 6 Exercise 6.2 Solutions – Ganita Manjari 2026

📘 NCERT Ganita Manjari (2026) 📚 CBSE 2026–27 🏆 Step-by-Step Solutions

Class 9 Maths Chapter 6 Exercise 6.2 Solutions

Area — Ganita Manjari 2026–27

Prepare with complete Class 9 Maths Exercise 6.2 Solutions based on the latest NCERT Ganita Manjari (2026). This exercise covers the area of triangles, parallelograms, trapeziums and rhombuses, along with Heron’s Formula, area ratios, median and midpoint applications, and geometry-based proofs. All eleven questions are explained in a clear, step-by-step CBSE answer-writing style.

📖
Exercise
6.2
❓
Questions
11 Questions
📐
Main Concept
Area &
Its Applications
🧮
Key Skill
Heron’s Formula &
Area Ratios
📊
Triangle Area
= ½ × b × h
🎯
Exam Importance
★★★★★
🎯 By the End of Exercise 6.2,
You Will Be Able To…
✅ Find the Area of Triangles
✅ Apply Heron’s Formula When Three Sides Are Known
✅ Calculate the Area of a Trapezium
✅ Solve Area Problems Involving Rhombuses
✅ Use the Area Formula for Parallelograms
✅ Solve Area-Ratio and Equal-Area Problems
✅ Apply Median and Midpoint Area Properties
✅ Solve Geometry Proofs Step by Step

📚 Table of Contents

📖 About Class 9 Maths Chapter 6 Exercise 6.2

Class 9 Maths Chapter 6 Exercise 6.2 Solutions cover Exercise Set 6.2 from Chapter 6 – Measuring Space: Perimeter and Area in the latest NCERT Ganita Manjari (2026–27) textbook. This page provides complete, reliable and easy-to-follow NCERT Class 9 Maths solutions for students searching for Class 9 Maths Exercise 6.2 Solutions, Exercise 6.2 Class 9 Maths answers and Class 9 Maths Chapter 6 Solutions in one place.

The NCERT Class 9 Maths Chapter 6 Exercise 6.2 Solutions are arranged question-wise in a clear, student-friendly CBSE answer-writing format. This exercise focuses on important questions related to area of triangles, area of trapeziums, Heron’s Formula, area of rhombuses, area of parallelograms, equal-area triangles, area ratios and geometry proofs. These solutions are useful for homework, classroom practice, self-study, revision and CBSE examination preparation.

🎯 Exercise Snapshot

📘 What You’ll Find
  • Complete coverage of Exercise Set 6.2.
  • NCERT-based solutions for all eleven questions.
  • Important questions on area, ratios and geometry proofs.
📚 Page Includes
  • Step-by-step NCERT Class 9 Maths Exercise 6.2 solutions.
  • Complete question-wise coverage of Class 9 Maths Chapter 6.
  • Simple and exam-oriented CBSE answer-writing approach.
🏆 Best For
  • Students following Ganita Manjari 2026–27.
  • Homework, classroom practice and assignments.
  • Revision and CBSE examination preparation.

🔎 Jump to Any Question

Quickly jump to any question from the 11 questions of Class 9 Maths Exercise Set 6.2.

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📚 Learn Before You Solve

✨ Class 9 Maths Chapter 6 Exercise 6.2 Solutions — पहले concept समझें, फिर solve करें

Before solving Class 9 Maths Chapter 6 Exercise 6.2 Solutions, first understand the important concepts behind area of triangles, area of trapeziums, Heron’s formula, semi-perimeter, area of a rhombus, equal-area triangles and area ratios.

This Learn Before You Solve section follows the NCERT Ganita Manjari Class 9 Mathematics approach and builds the concepts needed for Exercise Set 6.2.

The learning journey moves from basic area ideas to Heron’s formula, geometric area reasoning, circle connections, Brahmagupta’s formula and important special cases. The aim is simple: understand the mathematics first, then solve independently.

🔺 Understanding Area of a Triangle
Learn how base and perpendicular height determine area
In Class 9 Maths Chapter 6 Exercise 6.2 of NCERT Ganita Manjari, you will work with areas of triangles, trapeziums, rhombuses and figures formed using these ideas. The first step is to understand why the area of a triangle depends on its base and its perpendicular height.
📐 Begin with the Area of a Parallelogram

Take a parallelogram with base b and perpendicular height h. Its area is:

Area of parallelogram = b × h
A diagonal divides a parallelogram into two equal-area triangles
b h
🔺 Why Does the Triangle Have Half the Area?

The diagonal joins two opposite vertices of the parallelogram. It divides the parallelogram into two triangles. These two triangles have the same base and the same corresponding perpendicular height, so their areas are equal.

Therefore, the area of one triangle is exactly half the area of the parallelogram.

🧠 Build the Formula
Step 1 — Area of the parallelogram
Area = b × h
Step 2 — The diagonal makes two equal triangles
One triangle occupies half of the parallelogram.
Step 3 — Take half of b × h
Therefore, triangle area is half of the parallelogram area.
📌 Area of a Triangle
Area = 1 2 × b × h
b = base    |    h = perpendicular height
📏 What Exactly Is the Height?

The height is the perpendicular distance from the opposite vertex to the chosen base, or to the extension of that base.

Important: If you choose a different side as the base, you must use the perpendicular height corresponding to that base.
📐 When the Height Falls Outside

In an obtuse triangle, the perpendicular may meet the extension of the chosen base rather than the side itself. That perpendicular distance is still the correct height.

The formula remains unchanged because the important quantity is the perpendicular distance.

💡 Quick Example

A triangular garden has a base of 12 m and a perpendicular height of 7 m. What is its area?

Base = 12 m
Perpendicular height = 7 m
Area = 1 2 × 12 × 7 = 42 m²
💭 Think and Reflect — Class 9 Maths Chapter 6 Exercise 6.2
The “Thin” Parallelogram Problem

What happens if the parallelogram is “thin” and the foot of perpendicular from C to AD does not lie on side AD? The construction then does not seem to work. How do we fix this “gap”?

View Solution →
🔶 Area of a Trapezium
Understand how the two parallel sides and height determine area
A trapezium is a quadrilateral with one pair of parallel sides. To find its area, we need to understand how these two parallel sides work together with the perpendicular height. The key idea is to turn the trapezium into a shape whose area we already understand.
📐 First, Identify the Three Important Measurements

Suppose the parallel sides of a trapezium have lengths a and b. The perpendicular distance between them is its height h.

a b h
a and b are the parallel sides, while h is the perpendicular distance between them.
🧠 Why Do We Use the Average of the Parallel Sides?

The two parallel sides of a trapezium are generally different in length. So there is no single base that can be used directly as in a parallelogram.

The area depends on the combined effect of both parallel sides. Their average gives the effective base length for the trapezium.

🔎 Build the Formula
Step 1 — Find the average of the parallel sides
Average of parallel sides = a + b 2
Step 2 — Multiply by the perpendicular height
Area = average of parallel sides × perpendicular height
Step 3 — The trapezium-area formula
Area = a + b 2 × h
🔗 A Useful Connection with Triangle Area

You have just learned that the area of a triangle is based on base × perpendicular height. A trapezium follows the same basic idea: first determine its effective base from the two parallel sides, then multiply by the perpendicular height.

📌 Do the Four Side Lengths Always Tell Us the Area?

Not necessarily. To determine the area of a trapezium using the standard formula, we need the lengths of its two parallel sides and the perpendicular height.

The height is especially important because it measures the perpendicular distance between the parallel sides.

💡 Quick Example

A trapezium has parallel sides of lengths 14 cm and 8 cm. Its perpendicular height is 5 cm. Find its area.

Parallel sides = 14 cm and 8 cm
Height = 5 cm
Area = 14 + 8 2 × 5 = 11 × 5 = 55 cm²
🧮 Heron’s Formula: When Three Sides Are Known
Find the area of a triangle when its height is not given
In Class 9 Maths Chapter 6 Exercise 6.2 of NCERT Ganita Manjari, some area questions give the three sides of a triangle rather than its base and perpendicular height. In such cases, Heron’s Formula provides a direct way to find the area.
📐 Why Do We Need Heron’s Formula?

You already know that the area of a triangle can be found from its base and perpendicular height. But suppose the three sides are known and the height is not. Drawing the height and finding it separately may require additional work.

Heron’s Formula gives another route: the area can be calculated directly from the three side lengths.

When the three sides are known
a b c
Here the three side lengths are known, but the perpendicular height has not been supplied.
1️⃣ First Find the Semi-Perimeter

Heron’s Formula begins with the semi-perimeter, usually represented by s.

s = a + b + c 2
Semi-perimeter means half of the perimeter.
🧮 Heron’s Formula
Area = √ [ s(s − a)(s − b)(s − c) ]
where s is the semi-perimeter and a, b, c are the three side lengths.
🧠 The Heron’s Formula Flow
Step 1: Write the three side lengths.
Step 2: Find the semi-perimeter s.
Step 3: Substitute s and the three side lengths into Heron’s Formula.
Step 4: Simplify the expression to obtain the area in square units.
💡 Quick Example

Consider a triangle whose three sides are 5 cm, 6 cm and 7 cm.

Step 1:
s = 5 + 6 + 7 2 = 9 cm
Step 2:
Area = √[9(9 − 5)(9 − 6)(9 − 7)]
= √[9 × 4 × 3 × 2] = √216
= 6√6 cm²
🔗 Connect It to What You Already Know

Heron’s Formula is another way of finding the same area of a triangle. If the base and perpendicular height are easy to obtain, the usual triangle-area formula may be convenient. If all three sides are given, Heron’s Formula is especially useful.

🔢 Ratio → Sides → Area
Understand how a side ratio helps determine actual lengths
In Class 9 Maths Chapter 6 Exercise 6.2, some area problems give the sides of a triangle in a ratio instead of giving their actual lengths. The important skill is to convert the ratio into actual side lengths using the given perimeter, and then use the appropriate area method.
🔎 What Does a Side Ratio Tell Us?

Suppose the three sides of a triangle are in the ratio 2 : 3 : 4. This does not mean that the sides are 2 cm, 3 cm and 4 cm. It means that the sides are proportional to these numbers.

So the three sides can be written as:
2x,   3x,   4x
Here x is the common scale factor.
The ratio gives the relative sizes of the three sides
4x 3x 2x
🧠 How Do We Find the Actual Side Lengths?

If the perimeter is known, add the ratio parts first. Their total tells us how many equal parts make up the whole perimeter.

For the ratio 2 : 3 : 4:
Total ratio parts = 2 + 3 + 4 = 9
If the perimeter is 45 cm, each ratio part is 45 ÷ 9 = 5 cm.
Therefore, the sides are 10 cm, 15 cm and 20 cm.
📐 The Complete Reasoning Flow
Step 1 — Read the ratio
Identify how the side lengths compare.
Step 2 — Use the perimeter
Add the ratio parts and determine the value of one part.
Step 3 — Find the actual sides
Multiply each ratio number by the value of one part.
Step 4 — Choose the area method
If the three sides are now known and the height is not given, Heron’s Formula can be used.
💡 Quick Example

The sides of a triangular plot are in the ratio 2 : 3 : 4, and its perimeter is 45 m. Find the three side lengths.

Ratio parts: 2 + 3 + 4 = 9
One part: 45 upon 9 = 5 m
Side lengths:
2 × 5 = 10 m
3 × 5 = 15 m
4 × 5 = 20 m
🔗 Remember the Order

A ratio gives relative lengths, not actual lengths. Use the given perimeter to find the scale factor first. Only after finding the actual side lengths should you move on to the appropriate area calculation.

◇ Area of a Rhombus
Understand how the diagonals determine the area
In Class 9 Maths Chapter 6 Exercise 6.2 of NCERT Ganita Manjari, area questions may involve a rhombus and its diagonals. Before solving such questions, it is important to understand why the diagonals can be used to find the area of a rhombus.
📐 What Is Special About a Rhombus?

A rhombus is a parallelogram in which all four sides are equal. Like every parallelogram, it has two diagonals joining opposite vertices.

The important fact for area is that the diagonals of a rhombus bisect each other at right angles. This divides the rhombus into four right triangles.

The diagonals divide the rhombus into four right triangles
d₂ d₂ d₁ d₁ O
The two diagonals meet at their common midpoint and are perpendicular.
🧠 Build the Area from the Four Triangles

Let the diagonals of the rhombus be d₁ and d₂. Since they bisect each other, each half of a diagonal has length d₁ 2 or d₂ 2 .

Each of the four small triangles has a right angle at the intersection of the diagonals. Adding their areas gives the area of the whole rhombus.

📌 Area of a Rhombus
Area = d₁ × d₂ 2
d₁ and d₂ are the lengths of the two diagonals.
📌 What Information Do We Need?

If both diagonals are known, the area can be found directly using the diagonal formula.

If only the side length is known, that alone does not generally determine the area of a rhombus. Another measurement, such as a perpendicular height or suitable diagonal information, may be needed.

💡 Quick Example

A rhombus has diagonals of lengths 16 cm and 10 cm. Find its area.

Area = 16 × 10 2 = 80 cm²
🟩 Equal-Area Triangles
Understand when different triangles can have the same area
In Class 9 Maths Chapter 6 Exercise 6.2 of NCERT Ganita Manjari, some questions ask you to compare areas or prove that two triangles have equal areas. For these questions, calculating the area of each triangle separately is often unnecessary. The key is to recognise when triangles have the same base or equal bases and the same perpendicular height.
📐 Same Base + Same Height = Same Area

Recall the area formula: Area = half × base × perpendicular height. Therefore, if two triangles have the same base and their opposite vertices lie on a line parallel to that base, their perpendicular heights are equal.

Moving the vertex along a parallel line does not change the height
common base h h A B parallel line
🧠 Why Are Their Areas Equal?

Both triangles have the same base. Their third vertices lie on the same line parallel to that base, so the perpendicular distance from that line to the base is the same.

Same base + same perpendicular height
⇒ Equal areas
🔗 What If the Bases Are Different?

The same reasoning works when the bases are different but have equal lengths and the corresponding perpendicular heights are equal.

What matters is not where the triangle is drawn, but the two quantities in its area formula: the base and the perpendicular height.

📌 Equal Area Does Not Mean Congruent

Two triangles can have the same area even when they do not have the same shape or the same side lengths.

Equal area tells us that they cover the same amount of plane region. It does not by itself prove that the triangles are congruent.

🔍 Compare Areas Without Calculating Them

In geometry questions, you may not need to calculate numerical areas at all. Look for relationships first.

If two triangles have equal bases and equal corresponding heights, their areas are equal. This can immediately give an area relationship or ratio.
💭 Think and Reflect — Class 9 Maths Chapter 6 Exercise 6.2
Equal Area and Rearrangement

Since two triangles can have equal areas, you may wonder: Can we divide one triangle using straight cuts into two or more pieces and then rearrange those pieces to exactly cover the other triangle? What do you think? Is it possible?

View Solution →
💡 Quick Example

Two triangles each have a base of 10 cm. Their third vertices lie on the same line parallel to the base, 6 cm away from it.

Both triangles have:
Base = 10 cm
Perpendicular height = 6 cm
Therefore, their areas are equal.
📐 Area Ratios & Parallel-Line Reasoning
Understand how bases, heights and parallel lines help compare areas
In Class 9 Maths Chapter 6 Exercise 6.2 Solutions, area questions are not always about finding a numerical answer. Some problems require you to compare two or more regions or prove an area ratio. The easiest approach is to identify the common base, common height, or parallel lines before doing any calculation. This idea is especially useful in Ganita Manjari Class 9 Maths geometry problems involving equal areas, medians and parallel-line constructions.
🔍 First Ask: What Is Common?

Before comparing areas, look at the diagram carefully. Ask these three questions:

1. Same Base?
If the base is the same, compare the perpendicular heights.
2. Same Height?
If the heights are equal, compare the bases.
3. Parallel Lines?
Parallel lines can immediately give equal perpendicular heights.
📊 Same Height → Area Ratio Follows the Base Ratio

Suppose two triangles have the same perpendicular height. Their areas are determined by their bases because the factor half × height is common to both.

Area of Triangle 1 : Area of Triangle 2
= Base 1 : Base 2

So, if one base is twice the other while the heights are equal, the corresponding area is also twice as large.

↕️ Same Base → Area Ratio Follows the Height Ratio

The same reasoning works in the other direction. If two triangles have the same base, then their areas depend directly on their perpendicular heights.

Same base + different heights
→ Compare the heights to compare the areas.
∥ Why Parallel Lines Are So Useful

When two bases lie on one line and the opposite vertices lie on another line parallel to it, the perpendicular distance between the two parallel lines is fixed. Therefore, all such triangles have the same height with respect to that base line.

Different bases on one line, vertices on a parallel line
b₁ b₂ h P Q parallel line common base line
💡 Fresh Example: Compare Without Finding Both Areas

Two triangles have the same perpendicular height. Their bases are 8 cm and 12 cm.

Since the height is common, the area ratio is the same as the base ratio:
8 : 12 = 2 : 3
So the areas are in the ratio 2 : 3. There is no need to calculate either area separately.
🧠 How to Think in Geometry Proofs

When an Exercise 6.2 question asks you to prove an area equality or ratio, do not begin by measuring the diagram. Instead, identify the geometric relationship first:

Parallel lines → equal perpendicular distance
Equal perpendicular heights → compare bases
Equal bases → compare heights
Equal base + equal height → equal areas
✏️ Before You Solve

In an area-ratio or parallel-line problem, first mark the base and the corresponding perpendicular height. Once the common quantity is recognised, the required relationship often becomes much simpler.

🧠 NCERT Deep Dive: Triangle Area, Special Cases & Circle Connections
Go deeper into the proofs, checks and alternative area formulas
The Class 9 Maths Chapter 6 Exercise 6.2 concepts developed in NCERT Ganita Manjari go beyond memorising the area of a triangle and Heron’s formula. The textbook checks Heron’s formula in special triangles and connects triangle area with the circumcircle, incircle and perpendicular height.

This advanced section is for students who want to understand why the formulas agree, how special cases arise, and how different geometric ideas lead to the same area.
📐 1. Same Sides, Different Angle — Does the Area Stay the Same?

Imagine a parallelogram whose two adjacent side lengths remain fixed. Now increase or decrease the angle between those sides. The side lengths have not changed, but the perpendicular height changes.

Since the area of a parallelogram depends on its base and corresponding perpendicular height, changing the angle can change the area.

Important idea: Fixed side lengths do not automatically mean fixed area. The angle between the sides can affect the perpendicular height, and therefore the area.
🔺 2. The “Gap” for an Obtuse Triangle

For a right-angled triangle, enclosing the triangle inside a rectangle makes the half-area relationship easy to see. But what happens when the triangle is obtuse?

The perpendicular from the opposite vertex may fall on the extension of the base rather than on the base segment itself. The argument still works because the perpendicular distance to the line containing the base is the required height.

So remember:

Height means perpendicular distance from the vertex to the line containing the chosen base. It does not have to lie completely inside the triangle.
🧩 3. Another Way to Understand Triangle Area

NCERT gives another beautiful route to the triangle-area formula: take two congruent copies of a triangle and fit them together to form a parallelogram.

Area of parallelogram = base × height

The parallelogram consists of two congruent triangles. Therefore, the area of one triangle is half the area of the parallelogram.
Area of triangle = 1 2 × base × height
🔺 4. Equilateral Triangle — Heron Meets Pythagoras

Suppose all three sides of an equilateral triangle are a. Heron’s formula gives its area using only the side lengths.

Semi-perimeter:
s = 3a 2
Heron’s formula then gives
Area = √3 4 a²

NCERT then checks the result using the familiar half-base-times-height formula. Dropping the perpendicular from the vertex divides the equilateral triangle into two right triangles. Baudhāyana–Pythagoras gives the height, and the same area is obtained.

🔶 5. Isosceles Triangle — Another Check of Heron’s Formula

Consider an isosceles triangle with equal sides a and base 2b. Heron’s formula gives

Area = b√(a² − b²)

Now drop the perpendicular from the vertex to the base. In an isosceles triangle, this divides the base into two equal parts of length b.

Using Baudhāyana–Pythagoras:
h = √(a² − b²)
Therefore,
Area = 1 2 × 2b × √(a² − b²)
= b√(a² − b²)
The two methods agree.
📐 6. The 3–4–5 Triangle — Heron and Pythagoras Agree

For a triangle with side lengths 3, 4 and 5:

Semi-perimeter:
s = 6
Heron’s formula gives:
Area = √(6 × 3 × 2 × 1) = 6 square units

But the converse of the Baudhāyana–Pythagoras theorem tells us that a triangle with sides 3, 4 and 5 is right-angled. Therefore its area can also be checked directly using base 3 and height 4.

Area = 1 2 × 3 × 4 = 6 square units
🔬 7. How Is Heron’s Formula Proved?

NCERT points out that there are several proofs of Heron’s formula. One important route uses the Baudhāyana–Pythagoras theorem together with the repeated use of the difference-of-two-squares identity.

The important learning point is not to memorise the proof at this stage. Instead, understand that Heron’s formula is not an isolated rule: it can be derived from familiar geometric and algebraic results.
⭕ 8. Circumcircle and Incircle of a Triangle

NCERT now introduces two important circles associated with a triangle.

Circumcircle
The unique circle passing through all three vertices of a triangle.

Its radius is denoted by R.
Incircle
The unique circle that touches all three sides of a triangle.

Its radius is denoted by r.

If the sides of the triangle are a, b, c, NCERT gives two additional area formulas:

Area = abc 4R
Area = r a + b + c 2
The second formula has a particularly useful interpretation: the area of a triangle can be expressed using the inradius and the perimeter. NCERT notes that the proof of this formula uses a result that students will study in Grade 10.
🌟 One Triangle, Many Routes to Its Area
Base + perpendicular height
↓ Two congruent triangles → parallelogram
↓ Heron’s formula from three sides
↓ Special-case checks using Pythagoras
↓ Circumcircle and incircle → alternative area formulas
🧠 NCERT Deep Dive: Special Cases, Brahmagupta & Squaring a Rectangle
Go beyond the basic formulas and understand the mathematical connections in NCERT
NCERT Ganita Manjari Class 9 Maths goes beyond simply giving area formulas. These pages connect Brahmagupta’s formula, Heron’s formula, cyclic quadrilaterals, special cases and generalisation. The chapter also introduces the ancient Indian idea of squaring a rectangle through a geometric construction based on the Baudhāyana–Pythagoras theorem.

This advanced learning section supports students preparing Class 9 Maths Chapter 6 Exercise 6.2 Solutions. It is especially useful for students who want to understand not only the formulas, but also their connections, verification and proof.
⭕ 1. What Is a Cyclic 4-gon?

A cyclic 4-gon is a quadrilateral whose four vertices lie on the same circle. Let its four sides be represented by a, b, c, d. Its semi-perimeter is represented by s:

s = a + b + c + d 2
Cyclic quadrilateral ABCD inscribed in a circle for understanding Brahmagupta's formula
🧮 2. Brahmagupta’s Formula for a Cyclic 4-gon

For a cyclic 4-gon with side lengths a, b, c, d, first calculate its semi-perimeter:

s = a + b + c + d 2

Brahmagupta’s formula gives the area of the cyclic 4-gon:

Area = √[(s − a)(s − b)(s − c)(s − d)]

The important condition is that the quadrilateral must be cyclic. This formula is not a general formula for every quadrilateral having the same four side lengths.

▭ 3. Rectangle: Brahmagupta’s Formula Becomes ab

Every rectangle is cyclic. Let its side lengths be a and b. Its four sides are therefore a, b, a, b.

Semi-perimeter:
s = 2a + 2b 2 = a + b
Substituting in Brahmagupta’s formula:
Area = √[(a+b−a)(a+b−b)(a+b−a)(a+b−b)]
= √(b · a · b · a)
= ab
Thus, Brahmagupta’s formula gives the familiar rectangle area formula.
🔶 4. Isosceles Trapezium: A Beautiful Verification

Consider an isosceles trapezium whose parallel sides are 2a and 2b, while each non-parallel side has length c. Since every isosceles trapezium is cyclic, Brahmagupta’s formula applies.

2a 2b c c h

The semi-perimeter is

s = a + b + c

Substituting in Brahmagupta’s formula:

Area = (a+b)√[(c+b−a)(c+a−b)]

Using the difference-of-two-squares identity:

(c+b−a)(c+a−b) = c² − (a−b)²
Area = (a+b)√[c² − (a−b)²]
If a perpendicular is dropped from the upper vertex to the longer base, the resulting right triangle has:

Hypotenuse = c
Horizontal part = a − b

By the Baudhāyana–Pythagoras theorem:
h = √[c² − (a−b)²]
Hence,
Area = (a+b)h
Since the parallel sides are 2a and 2b, this is exactly the familiar trapezium formula:
Area = 2a + 2b 2 × h = (a+b)h
🌱 5. Special Cases and Generalisation

A special case is obtained when a general result is applied under an additional condition. The resulting formula is simpler because the figure has extra properties. A general result that includes many special cases is called a generalisation.

Example 1: A square is a special case of a rectangle. In a rectangle, Area = length × breadth. If both lengths are equal to a, then Area = a².
Example 2: An isosceles right-angled triangle is a special case of a right-angled triangle. If its equal perpendicular sides are both a, then
a² + a² = c²
c = a√2
NCERT also shows this idea through algebraic identities. A more general identity may reduce to a simpler identity when one variable is given a particular value.

The mathematical flow is:
General result → Special case
Special case → helps us understand the general result
🔗 6. Brahmagupta’s Formula Generalises Heron’s Formula

A triangle with side lengths a, b, c can be viewed as a special case of a 4-gon by taking the fourth side to have zero length. Thus, d = 0.

The semi-perimeter of the 4-gon becomes:
s = a + b + c + 0 2 = a + b + c 2
This is exactly the semi-perimeter used in Heron’s formula.

Now substitute d = 0 in Brahmagupta’s formula:

Area = √[(s−a)(s−b)(s−c)(s−0)]
= √[s(s−a)(s−b)(s−c)]
This is Heron’s formula.
Therefore, Heron’s formula can be viewed as a special case of Brahmagupta’s formula.
◻️ 7. Squaring a Rectangle

In ancient mathematics, to square a shape means to construct a square having the same area as that shape. NCERT introduces a construction attributed to the ancient Indian mathematician Baudhāyana for a rectangle.

Suppose the rectangle has sides a and b, where a > b. Its area is ab square units. The aim is to construct a square whose area is also ab square units.
📐 8. Baudhāyana’s Rectangle-Squaring Construction

The construction in NCERT can be understood through the following sequence:

Step 1
Start with rectangle ABCD where AD = a and AB = b.
Step 2
Locate E on AD so that AE = AB = b.
Step 3
Locate the midpoint F of ED.
Step 4
Construct square AFGH with AF as its side and H lying on the extension of AB.
Step 5
With centre H and radius HG, draw an arc cutting BC at K.
Step 6
Draw through K a line parallel to AH and let it meet the produced diagonal AG at P.
Step 7
Construct square HPQS with HP as its side. This square has the same area as rectangle ABCD.
🔎 Understanding the Construction
H P G B K C S Q A E F D b a Fig. 6.30: Rectangle ABCD with AD = a, AB = b
🔬 9. Why Does the Construction Work?

Since AE = b and AD = a,

ED = a − b

Since F is the midpoint of ED,

EF = a − b 2

Also, AF is half of AE + AD:

AF = a + b 2

Since AFGH is a square, HG = AF. Also, HK is the radius of the circle with centre H. Therefore,

HK = a + b 2

The vertical distance from H to the original base line is

BH = a − b 2

In right-angled triangle HKP, by the Baudhāyana–Pythagoras theorem:

HP² = HK² − BH²
= (a + b)² 4 − (a − b)² 4
🧩 10. The Algebra Behind the Geometry

Expand the two squares:

(a+b)² = a² + 2ab + b²
(a−b)² = a² − 2ab + b²

Therefore,

HP² = a² + 2ab + b² 4 − a² − 2ab + b² 4
= 4ab 4 = ab
HP² = ab
Therefore, the area of square HPQS is ab square units.
The area of rectangle ABCD is also ab square units.
Hence, both figures have equal areas.
🌟 The Bigger Mathematical Picture

These NCERT pages are not a collection of unrelated formulas. They show how mathematics develops by connecting general results, special cases, geometry and algebra.

Brahmagupta’s formula
↓ Special case: fourth side becomes zero
↓ Heron’s formula

Rectangle area = ab
↓ Geometric construction of an equal-area square
↓ Baudhāyana–Pythagoras theorem + algebraic identity

The deeper lesson is that a mathematical formula becomes meaningful when we understand where it comes from, how it connects to other results, and why it works in special cases.

⚡ Quick Revision Dashboard
Revise the formulas, proofs and key relationships before solving Exercise 6.2
Before solving Class 9 Maths Chapter 6 Exercise 6.2, quickly revise the formulas and geometric relationships developed throughout the NCERT Ganita Manjari chapter.

Do not choose a formula by memory alone. First identify what information the figure gives you: base, height, parallel sides, three sides, diagonals, equal lengths, ratios or a special geometric property.
1. 🔺 Triangle Area
Use the chosen base and its corresponding perpendicular height.
Area = 1 2 × b × h
b = base, h = perpendicular height
2. ▱ Parallelogram Area
Area depends on the base and the perpendicular distance between the parallel sides.
Area = b × h
Changing the angle can change h, even when the two side lengths stay fixed.
3. 🔶 Trapezium Area
a and b are the parallel sides; h is their perpendicular distance.
Area = a + b 2 × h
4. 🧮 Semi-Perimeter
For a triangle with sides a, b, c:
s = a + b + c 2
5. 🧮 Heron’s Formula
Use when the three sides of a triangle are known.
Area = √[s(s − a)(s − b)(s − c)]
6. ◇ Rhombus Area
Its diagonals bisect each other at right angles.
Area = d₁ × d₂ 2
7. ⚖️ Equal-Area Rule
If two triangles have the same base and same perpendicular height:
Equal base + equal height
⇒ Equal area
8. 📐 Area-Ratio Rule
For triangles having the same height:
Area ratio = Base ratio
Same base → area ratio = height ratio
🔬 Advanced Triangle Formula Revision
🔺 Equilateral Triangle
If each side is a:
Area = √3 4 a²
Heron’s formula and half-base-times-height give the same result.
🔶 Isosceles Triangle
Equal sides = a, base = 2b.
h = √(a² − b²)
Area = b√(a² − b²)
📐 3–4–5 Triangle
Since 3² + 4² = 5², the triangle is right-angled.
Area = 6 square units
Heron’s formula gives the same answer.
⭕ Triangle Area Through Its Circles
O I R r A B C c b a T
Circumcircle Formula
If the sides are a, b, c and circumradius is R:
Area = abc 4R
Incircle Formula
If the inradius is r:
Area = r a + b + c 2
🔷 Cyclic 4-gon & Brahmagupta’s Formula
B A D C a d c b
Condition: Brahmagupta’s formula applies to a cyclic 4-gon — a quadrilateral whose four vertices lie on one circle.
Semi-Perimeter
s = a + b + c + d 2
Brahmagupta’s Formula
Area = √[(s−a)(s−b)(s−c)(s−d)]
▭ Rectangle
A rectangle is a cyclic 4-gon.
Area = ab
Brahmagupta reduces to the familiar formula.
🔶 Isosceles Trapezium
Parallel sides = 2a and 2b; equal sides = c.
h = √[c² − (a−b)²]
Area = (a+b)√[c² − (a−b)²]
🔗 Brahmagupta → Heron
Treat a triangle as a special case of a 4-gon with d = 0.
Area = √[s(s−a)(s−b)(s−c)]
This is Heron’s formula.
◻️ Squaring a Rectangle — Essential Formula
a b → side = √ab equal area = ab
To square a rectangle means to construct a square having the same area as the rectangle. For a rectangle with sides a and b:
Area of rectangle = ab
Side of equal-area square = √ab
a+b 2 ² − a−b 2 ² = ab
Proof connection: The construction uses a right-angled triangle and the Baudhāyana–Pythagoras theorem. The final algebraic simplification comes from the difference of two squares.
🧠 Master Formula Connections
Base + height → triangle area
Three sides → semi-perimeter → Heron’s formula
Special triangle → Heron’s formula can be checked using Pythagoras and half-base-times-height
Triangle + circumcircle → area using R
Triangle + incircle → area using r and perimeter
Four sides + cyclic condition → Brahmagupta’s formula
Cyclic 4-gon + special shape → familiar formulas for rectangle and isosceles trapezium
Brahmagupta + d = 0 → Heron’s formula
Rectangle → equal-area square → Baudhāyana construction → Pythagoras + algebra
🎯 Before You Solve: 7-Second Formula Check
1. Is a base and perpendicular height given? → Triangle / parallelogram idea
2. Are two parallel sides and height given? → Trapezium
3. Are three triangle sides given? → Heron’s formula
4. Are diagonals of a rhombus given? → Diagonal formula
5. Are equal bases/heights or parallel lines involved? → Equal-area / area-ratio reasoning
6. Are four sides given with a cyclic condition? → Brahmagupta
7. Is the problem about constructing a square with the same area as a rectangle? → Baudhāyana construction

📝 Class 9 Maths Chapter 6 Exercise 6.2 Solutions

Solve all eleven questions of Class 9 Maths Chapter 6 Exercise 6.2 with clear, step-by-step NCERT Ganita Manjari (2026–27) solutions. This exercise covers important questions on area of triangles, trapeziums, rhombuses and parallelograms, along with Heron’s Formula, area ratios, equal-area triangles, medians, midpoints and geometry proofs. Each question is presented in a simple, student-friendly CBSE answer-writing format.

📝 Step-by-Step Solutions 🎯 NCERT & CBSE Aligned ⭐ Complete Exercise 6.2
Chapter 6 • Exercise Set 6.2 • Question 1

Class 9 Maths Chapter 6 Exercise Set 6.2 Question 1 – Solution

Ganita Manjari 2026–27 | Measuring Space: Perimeter and Area
Find the area of triangle ADE in Fig. 6.31.
Class 9 Maths Chapter 6 Exercise Set 6.2 Question 1 – Fig. 6.31 Figure 6.31 shows triangle ADE inside rectangle ABCD. The rectangle has length 10 cm and height 8 cm. The perpendicular height of triangle ADE is 10 cm and its base AD is 8 cm. A B D C E 10 cm 8 cm
Fig. 6.31 – Triangle ADE inside rectangle ABCD
Given
From Fig. 6.31, ABCD is a rectangle.
AD = BC = 8 cm
AB = DC = 10 cm
Taking AD as the base, the perpendicular distance from E to AD is equal to DC.
Therefore, perpendicular height = 10 cm

To Find: Area of triangle ADE
Solution
We know that,

Area of a triangle = 1 2 × Base × Height

Therefore,

Area of △ADE = 1 2 × 8 × 10

= 4 × 10

= 40 cm²
∴ The area of triangle ADE is 40 cm².
Chapter 6 • Exercise Set 6.2 • Question 2

Class 9 Maths Chapter 6 Exercise Set 6.2 Question 2 – Solution

Ganita Manjari 2026–27 | Measuring Space: Perimeter and Area
The parallel sides of a trapezium are 40 cm and 20 cm. If its non-parallel sides are both equal, each being 26 cm, find the area of the trapezium.
Isosceles trapezium with parallel sides 40 cm and 20 cm An isosceles trapezium ABCD has parallel sides AB equal to 20 cm and DC equal to 40 cm. Its non-parallel sides AD and BC are each 26 cm. The perpendicular height is shown as h. A B C D 20 cm 40 cm 26 cm 26 cm h
Isosceles trapezium with parallel sides 40 cm and 20 cm
Given
The parallel sides of the trapezium are:
40 cm and 20 cm
The two non-parallel sides are equal, each measuring:
26 cm

To Find: Area of the trapezium
Solution
Since the two non-parallel sides are equal, the trapezium is an isosceles trapezium.

Draw perpendiculars from the endpoints of the shorter parallel side to the longer parallel side.

The difference between the parallel sides is:

40 − 20 = 20 cm

In an isosceles trapezium, this difference is divided equally on both sides.

Therefore, the horizontal part of each right-angled triangle is:

20 2 = 10 cm

Let the perpendicular height of the trapezium be h.

Using Pythagoras’ theorem in the right-angled triangle:

h² + 10² = 26²

h² + 100 = 676

h² = 676 − 100

h² = 576

h = √576 = 24 cm

Now, the area of a trapezium is:

Area = 1 2 × Sum of parallel sides × Height

Therefore,

Area of trapezium = 1 2 × (40 + 20) × 24

= ½ × 60 × 24

= 30 × 24

= 720 cm²
∴ The area of the trapezium is 720 cm².
Chapter 6 · Exercise Set 6.2 · Question 3

Class 9 Maths Chapter 6 Exercise Set 6.2 Question 3 – Solution

Ganita Manjari 2026–27 | Measuring Space: Perimeter and Area
Find the area of a triangle, given that its sides are 8 cm and 11 cm long, and its perimeter is 32 cm.
Given
Two sides of the triangle are:
8 cm and 11 cm
Perimeter of the triangle = 32 cm

To Find: Area of the triangle
Solution
Let the third side of the triangle be x cm.

Since the perimeter of a triangle is the sum of its three sides,

x + 8 + 11 = 32

x + 19 = 32

x = 32 − 19

x = 13 cm

Thus, the three sides of the triangle are:

8 cm, 11 cm and 13 cm

We use Heron’s formula to find the area of the triangle.

Heron’s formula is:

Area = √[ s(s − a) (s − b) (s − c) ]

where s is the semi-perimeter.

Semi-perimeter,

s = 8 + 11 + 13 2

= 32 2 = 16 cm

Now, using Heron’s formula,

Area = √[16(16 − 8)(16 − 11)(16 − 13)]

= √[16 × 8 × 5 × 3]

= √1920

= √(64 × 30)

= 8√30 cm²

Therefore, the area of the triangle is approximately:

8√30 ≈ 43.82 cm²
∴ The area of the triangle is 8√30 cm² or approximately 43.82 cm².
Chapter 6 · Exercise Set 6.2 · Question 4

Class 9 Maths Chapter 6 Exercise Set 6.2 Question 4 – Solution

Ganita Manjari 2026–27 | Measuring Space: Perimeter and Area
The sides of a triangular plot are in the ratio 3 : 5 : 7; its perimeter is 300 m. Find its area.
Given
The sides of the triangular plot are in the ratio:
3 : 5 : 7
Perimeter of the triangular plot = 300 m

To Find: Area of the triangular plot
Solution
Let the three sides of the triangular plot be:

3x, 5x and 7x

Since the perimeter is 300 m,

3x + 5x + 7x = 300

15x = 300

x = 300 15 = 20

Therefore, the three sides are:

3x = 3 × 20 = 60 m
5x = 5 × 20 = 100 m
7x = 7 × 20 = 140 m

The semi-perimeter is:

s = 60 + 100 + 140 2

= 300 2 = 150 m

Using Heron’s formula,

Area = √[ s(s − a) (s − b) (s − c) ]

Area = √[150(150 − 60)(150 − 100)(150 − 140)]

= √(150 × 90 × 50 × 10)

= √6,750,000

= √(2,250,000 × 3)

= 1500√3 m²

Therefore,

Area ≈ 1500 × 1.732

≈ 2598.08 m²
∴ The area of the triangular plot is 1500√3 m², or approximately 2598.08 m².
Chapter 6 · Exercise Set 6.2 · Question 5

Class 9 Maths Chapter 6 Exercise Set 6.2 Question 5 – Solution

Ganita Manjari 2026–27 | Measuring Space: Perimeter and Area
One diagonal of a rhombus is twice as long as the other diagonal. If the rhombus has area 128 cm², find the length of the shorter diagonal.
Area of Rhombus = 128 cm²
Given
Area of the rhombus = 128 cm²
One diagonal is twice the other diagonal.

To Find: Length of the shorter diagonal
Solution
Let the shorter diagonal of the rhombus be d cm.

Therefore, the longer diagonal is 2d cm.

We know that the area of a rhombus is:

Area = 1 2 × Diagonal 1 × Diagonal 2

Therefore,

128 = 1 2 × d × 2d

128 = d²

Therefore,

d² = 128

d = √128

d = √(64 × 2)

d = 8√2 cm
∴ The length of the shorter diagonal is 8√2 cm.
Chapter 6 · Exercise Set 6.2 · Question 6

Class 9 Maths Chapter 6 Exercise Set 6.2 Question 6 – Solution

Ganita Manjari 2026–27 | Measuring Space: Perimeter and Area
ABCD is a parallelogram. P and Q are any two points on side AB. What can you say about the ratio of the areas (△PCD) : (△QCD)?
Area (△PCD) : Area (△QCD) = ?
Parallelogram ABCD with points P and Q on side AB Parallelogram ABCD has two points P and Q on its side AB. Triangles PCD and QCD have the same base CD and equal perpendicular heights. A B C D P Q CD h
Triangles PCD and QCD have the same base CD and equal heights
Given
ABCD is a parallelogram.
P and Q are any two points on side AB.
Triangles PCD and QCD have the same base CD.

To Find:
Area (△PCD) : Area (△QCD)
Solution
Triangles PCD and QCD have the same base CD.

Also, P and Q lie on the line AB.

Since ABCD is a parallelogram,

AB ∥ CD

Therefore, the perpendicular distances of P and Q from the line CD are equal to the height of the parallelogram.

Let the common base be CD = b and the common height be h.

Area of △PCD = 1 2 × b × h

Area of △QCD = 1 2 × b × h

Hence,

Area (△PCD) : Area (△QCD)

= ½ × b × h ½ × b × h

= 1 : 1
∴ The ratio of the areas is Area (△PCD) : Area (△QCD) = 1 : 1.
Thus, the two triangles have equal areas.
Chapter 6 · Exercise Set 6.2 · Question 7

Class 9 Maths Chapter 6 Exercise Set 6.2 Question 7 – Solution

Ganita Manjari 2026–27 | Measuring Space: Perimeter and Area
O is any point on the diagonal PR of a parallelogram PQRS. Prove that the areas of triangles PSO and PQO are equal.
Area (△PSO) = Area (△PQO)
Parallelogram PQRS with O on diagonal PR Parallelogram PQRS has diagonals PR and SQ intersecting at M. Point O lies on diagonal PR between P and M. P Q R S O M
Parallelogram PQRS with O on diagonal PR and diagonals intersecting at M
Given
PQRS is a parallelogram.
O is any point on diagonal PR.
Diagonals PR and SQ intersect at M.

To Prove:
Area (△PSO) = Area (△PQO)
Solution
Since PQRS is a parallelogram, its diagonals bisect each other.

Therefore,

SM = QM

In △PSQ, M is the midpoint of SQ.

Hence, PM is a median of △PSQ.

We know that a median of a triangle divides it into two triangles of equal area.

Therefore,

Area (△PSM) = Area (△PQM) ……… (1)

Now, in △OSQ, M is also the midpoint of SQ.

Hence, OM is a median of △OSQ.

Therefore,

Area (△OSM) = Area (△OQM) ……… (2)

Since O lies on PM,

Area (△PSM) = Area (△PSO) + Area (△OSM)

Similarly,

Area (△PQM) = Area (△PQO) + Area (△OQM)

Using equations (1) and (2), we get:

Area (△PSO) + Area (△OSM) = Area (△PQO) + Area (△OQM)

But,

Area (△OSM) = Area (△OQM)

Subtracting these equal areas from both sides, we obtain:

Area (△PSO) = Area (△PQO)
∴ The areas of triangles PSO and PQO are equal.
Area (△PSO) = Area (△PQO)
Hence proved.
Chapter 6 · Exercise Set 6.2 · Question 8

Class 9 Maths Chapter 6 Exercise Set 6.2 Question 8 – Solution

Ganita Manjari 2026–27 | Measuring Space: Perimeter and Area
If the mid-points of the sides of a 4-gon are joined in order, prove that the area of the parallelogram thus formed will be half of the area of the given 4-gon.
Area (PQRS) = ½ × Area (ABCD)
Quadrilateral ABCD with midpoints joined to form parallelogram PQRS P, Q, R and S are the midpoints of AB, BC, CD and DA. Joining them in order forms parallelogram PQRS inside quadrilateral ABCD. A B C D P Q R S
P, Q, R and S are the midpoints of AB, BC, CD and DA
Given
ABCD is a 4-gon (quadrilateral).
P, Q, R and S are the midpoints of AB, BC, CD and DA, respectively.

Construction:
Join BD and BS.

To Prove:
Area (PQRS) = ½ × Area (ABCD)
Solution
We know that the median of a triangle divides it into two triangles of equal areas.

In △BAD, S is the midpoint of AD.

Therefore, BS is a median of △BAD.

Hence,

Area (△BAS) = ½ × Area (△BAD)

……… (1)

In △BAS, P is the midpoint of AB.

Therefore, SP is a median of △BAS.

Hence,

Area (△APS) = ½ × Area (△BAS)

……… (2)

From (1) and (2),

Area (△APS)
= ½ × ½ × Area (△BAD)

= ¼ × Area (△BAD)

……… (3)

Similarly, in △BCD, Q and R are the midpoints of BC and CD.

Therefore,

Area (△CQR) = ¼ × Area (△BCD)

……… (4)

Adding (3) and (4),

Area (△APS) + Area (△CQR)
= ¼ × Area (△BAD) + ¼ × Area (△BCD)

= ¼ × Area (ABCD)

……… (5)

Similarly,

Area (△DRS) + Area (△BQP)
= ¼ × Area (ABCD)

……… (6)

Adding (5) and (6),

Area (△APS) + Area (△CQR) + Area (△DRS) + Area (△BQP)
= ¼ × Area (ABCD) + ¼ × Area (ABCD)

= ½ × Area (ABCD)

……… (7)

From the figure,

Area (△APS) + Area (△CQR) + Area (△DRS) + Area (△BQP) + Area (PQRS)
= Area (ABCD)

Using (7),

½ × Area (ABCD) + Area (PQRS)
= Area (ABCD)

Therefore,

Area (PQRS)
= Area (ABCD) − ½ × Area (ABCD)

= ½ × Area (ABCD)
∴ The area of the parallelogram PQRS is half the area of the given 4-gon ABCD.

Area (PQRS) = ½ × Area (ABCD)

Hence proved.
Chapter 6 • Exercise Set 6.2 • Question 9

Class 9 Maths Chapter 6 Exercise Set 6.2 Question 9 – Solution

Ganita Manjari 2026–27 | Measuring Space: Perimeter and Area
In △ABC, the midpoint of BC is D (Fig. 6.32). Median AD is drawn. P is any point on AD. Show that area (△ABP) = area (△ACP).
Figure 6.32 showing triangle ABC, median AD and point P on AD Triangle ABC has D as the midpoint of BC. AD is the median. P is any point on AD. Segments PB and PC are drawn to show the equal-area triangles PBD and PCD. A B C D P BD DC Median AD
Fig. 6.32 – Triangle ABC with median AD and point P on AD
Given
In △ABC, D is the midpoint of BC.
Therefore, BD = DC.
AD is a median of △ABC.
P is any point on AD.

To Show: Area (△ABP) = Area (△ACP)
Solution
Since AD is a median of △ABC, it divides △ABC into two triangles of equal area.

Therefore,

Area (△ABD) = Area (△ACD)

Also, D is the midpoint of BC. Hence,

BD = DC

Now, triangles PBD and PCD have equal bases BD and DC. They also have the same perpendicular height from P to BC.

Therefore,

Area (△PBD) = Area (△PCD)

Since,

Area (△ABD) = Area (△ACD)

We can write,

Area (△ABP) + Area (△PBD) = Area (△ACP) + Area (△PCD)

Since,

Area (△PBD) = Area (△PCD)

Cancelling the equal areas of △PBD and △PCD from both sides, we get,

Area (△ABP) = Area (△ACP)

Hence proved.
∴ The area of triangle ABP is equal to the area of triangle ACP.
Chapter 6 • Exercise Set 6.2 • Question 10

Class 9 Maths Chapter 6 Exercise Set 6.2 Question 10 – Solution

Ganita Manjari 2026–27 | Measuring Space: Perimeter and Area
Given a square ABCD, let P be a point within it. Join PA, PB, PC, PD (Fig. 6.33). What is the ratio of the areas of the red region (△PAB and △PCD) and the green region (△PBC and △PDA)?
Figure 6.33 showing square ABCD divided into red and green regions Square ABCD contains an interior point P. Segments PA, PB, PC and PD divide the square into four triangular regions. Triangles PAB and PCD form the red region, while triangles PBC and PDA form the green region. A D B C P Fig. 6.33
Fig. 6.33 – Square ABCD divided into red and green triangular regions
Given
ABCD is a square.
P is a point within the square.
PA, PB, PC and PD are joined.
Let the side of the square be a.

To Find: Ratio of the areas of the red region and the green region
Solution
Let the side of square ABCD be a.

Draw perpendiculars from P to the four sides of the square.

Let the perpendicular distances from P to AB, CD, AD and BC be h₁, h₂, h₃ and h₄, respectively.
Square ABCD with perpendicular distances h1, h2, h3 and h4 from P Square ABCD contains an interior point P. Segments PA, PB, PC and PD divide the square into four triangular regions. Dotted perpendicular lines from P to the four sides are labelled h1, h2, h3 and h4. A D B C P h₁ h₂ h₃ h₄
Perpendicular distances from P to the four sides of square ABCD
Since AB and CD are opposite sides of the square, the distance between them is equal to the side of the square.

Therefore,

h₁ + h₂ = a

Similarly, AD and BC are opposite sides of the square. Hence,

h₃ + h₄ = a

The red region consists of triangles PAB and PCD.

Therefore,

Area of red region = Area (△PAB) + Area (△PCD)

= 1 2 × AB × h₁ + 1 2 × CD × h₂

Since AB = CD = a,

= 1 2 × a × h₁ + 1 2 × a × h₂

= 1 2 × a × (h₁ + h₂)

= 1 2 × a × a

= a²/2

The green region consists of triangles PBC and PDA.

Therefore,

Area of green region = Area (△PBC) + Area (△PDA)

= 1 2 × BC × h₄ + 1 2 × AD × h₃

Since BC = AD = a,

= 1 2 × a × h₄ + 1 2 × a × h₃

= 1 2 × a × (h₃ + h₄)

= 1 2 × a × a

= a²/2

Hence,

Area of red region = Area of green region

Therefore,

Ratio of the areas of the red region and the green region

= a²/2 : a²/2

= 1 : 1
∴ The ratio of the areas of the red region and the green region is 1 : 1.
Chapter 6 • Exercise Set 6.2 • Question 11

Class 9 Maths Chapter 6 Exercise Set 6.2 Question 11 – Solution

Ganita Manjari 2026–27 | Measuring Space: Perimeter and Area
In △ABC, D is the midpoint of AB. P is any point on BC, and Q is a point on AB such that CQ ∥ PD. PQ is joined (Fig. 6.34). Prove that Area (△BPQ) = ½ Area (△ABC).
Fig. 6.34 – Triangle ABC with D as midpoint of AB, P on BC and Q on AB Triangle ABC contains D and Q on AB and P on BC. PD and CQ are parallel dashed lines, and PQ is joined. B A C D Q P
Fig. 6.34 – Triangle ABC with D as the midpoint of AB and CQ ∥ PD
Solution
Given
In △ABC, D is the midpoint of AB.
Therefore,
AD = DB
P is any point on BC.
Q is a point on AB such that:
CQ ∥ PD
PQ is joined.

To Prove:
Area (△BPQ) = ½ Area (△ABC)
Construction
Join CD.
Proof
Proof figure for Question 11 showing triangles PDC and PDQ Triangle ABC has D as the midpoint of AB, P on BC and Q on AB. CD is joined. PD and CQ are parallel, so triangles PDC and PDQ have the same base PD and equal perpendicular heights. B A C D Q P △PDC △PDQ Common base PD
Proof figure – CD is joined and CQ ∥ PD
Since D is the midpoint of AB,

AD = DB

Triangles △ACD and △BCD have equal bases AD and DB on the same straight line AB.

Their perpendicular heights from C to AB are equal.

Therefore,

Area (△ACD) = Area (△BCD)

Also,

Area (△ACD) + Area (△BCD) = Area (△ABC)

Hence,

Area (△BCD) = ½ Area (△ABC)

Now, triangle BCD is divided into two triangles BPD and PDC.

Therefore,

Area (△BCD) = Area (△BPD) + Area (△PDC)

Since CQ ∥ PD, triangles △PDC and △PDQ lie between the same parallel lines.

They have the same base PD and equal perpendicular heights.

Therefore,

Area (△PDC) = Area (△PDQ)

Now, triangle BPQ is divided into triangles BPD and PDQ.

Thus,

Area (△BPQ) = Area (△BPD) + Area (△PDQ)

Using,

Area (△PDQ) = Area (△PDC)

We get,

Area (△BPQ) = Area (△BPD) + Area (△PDC)

Therefore,

Area (△BPQ) = Area (△BCD)

But,

Area (△BCD) = ½ Area (△ABC)

Hence,

Area (△BPQ) = ½ Area (△ABC)
∴ Area (△BPQ) = ½ Area (△ABC)
Hence proved.

📚 Continue Learning

Congratulations! You have completed the Class 9 Maths Chapter 6 Exercise 6.2 Solutions. You have now worked through Exercise 6.2 of Chapter 6 – Measuring Space: Perimeter and Area. Continue your learning journey by revisiting Exercise 6.2 for revision, moving to the next exercise, or exploring other Class 9 Maths Chapter 6 Solutions.


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❓ Frequently Asked Questions

Find quick answers to common questions about Class 9 Maths Chapter 6 Exercise 6.2 Solutions. These FAQs explain what the exercise covers, which topics are included, how to approach different question types, and how to use the solutions effectively for homework, revision, self-study and CBSE examination preparation.

What is taught in Class 9 Maths Chapter 6 Exercise 6.2?

Exercise 6.2 of Class 9 Maths Chapter 6, Measuring Space: Perimeter and Area, focuses on different applications of area. The exercise includes questions based on area of triangles, trapeziums, rhombuses and parallelograms, Heron’s Formula, area ratios, equal-area triangles, medians, midpoints and geometry proofs.

How many questions are included in Exercise Set 6.2?

Exercise Set 6.2 contains 11 questions. These questions cover direct area calculations, Heron’s Formula, area ratios, equal-area figures and proof-based geometry questions. The Class 9 Maths Exercise 6.2 Solutions on this page follow the same question-wise order as the textbook.

Which important topics are covered in Exercise 6.2?

The important topics include area of a triangle, area of a trapezium, Heron’s Formula, area of a rhombus, area of a parallelogram, equal-area triangles, median and midpoint properties, area ratios and geometry proofs. These topics are useful for classroom practice, revision and CBSE examination preparation.

When should I use Heron’s Formula in Class 9 Maths Exercise 6.2?

Heron’s Formula is used when the three sides of a triangle are known and its area is required. In Exercise 6.2, students also use the formula in questions where the perimeter and a ratio of the sides are given. The sides must first be identified correctly before applying the formula.

How do I solve area questions involving a trapezium or rhombus?

First identify the required measurements from the question or figure. For a trapezium, focus on its parallel sides and height. For a rhombus, identify its diagonals or the other information provided. Convert all measurements into consistent units and write the required formula before substitution. The solutions explain each question in a clear, step-by-step format.

How are area-ratio questions solved in Exercise 6.2?

In area-ratio questions, first identify the figures being compared. Then use their common base, common height, corresponding sides or given geometric relationships. Areas are compared only after the relevant measurements and relationships have been established. Questions involving triangles, parallelograms, medians and parallel lines are included in this exercise.

How should I write geometry proofs in Class 9 Maths Exercise 6.2?

For a geometry proof, begin by identifying the given information and the result to be proved. Use suitable properties of triangles, parallelograms, medians, midpoints and parallel lines. Write each step in a logical order and mention the reason wherever necessary. The proof-based questions in Class 9 Maths Chapter 6 Exercise 6.2 Solutions are presented in a clear, exam-oriented format.

Are these Class 9 Maths Chapter 6 Exercise 6.2 Solutions based on Ganita Manjari 2026?

Yes. These Class 9 Maths Chapter 6 Exercise 6.2 Solutions are prepared according to the questions and concepts of the NCERT Ganita Manjari (2026–27) textbook. The solutions are arranged question-wise in a simple, student-friendly format to help with classwork, homework, self-study, revision and CBSE examination preparation.

📚 Useful Learning Resources

Continue your preparation with more Class 9 Maths resources from Maths Gurukulam, or visit the official NCERT and CBSE websites for the latest textbooks, syllabus, and academic updates.

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Found Class 9 Maths Chapter 6 Exercise 6.2 Solutions helpful? For students who need personal support beyond self-study, join Newton Study Point for concept-based Maths coaching by an experienced teacher. Small batches, individual attention, regular tests, and complete CBSE exam preparation are available for Classes 8, 9, 10, 11 & 12.

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Rakesh Kumar Singh - Mathematics Educator
👨‍🏫 Reviewed & Prepared By

Rakesh Kumar Singh

Mathematics Educator • Founder of Maths Gurukulam & Newton Study Point
18+ Years of Mathematics Teaching Experience • Teaching Since 2006

These Class 9 Maths Chapter 6 Exercise 6.2 Solutions are carefully prepared according to the latest NCERT Ganita Manjari (2026) and the CBSE curriculum. The solutions follow a clear, step-by-step approach to help students understand questions based on area of triangles, area of trapeziums, Heron’s formula, area of rhombuses, equal-area triangles, and practical applications of area, while building confidence in solving Exercise 6.2 problems.

📘 NCERT Ganita Manjari (2026) 🎯 CBSE Aligned 📝 Step-by-Step Solutions 💡 Concept-Based Learning
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