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NCERT Solutions for Class 6 Maths Chapter 6: Perimeter and Area — Free PDF

Complete step-by-step solutions for all exercises in NCERT Class 6 Maths Chapter 6. Learn formulas for perimeter and area of squares, rectangles, triangles, and composite shapes.

CBSEClass 6
The SparkEd Authors (IITian & Googler)15 March 202613 min read
NCERT Solutions Class 6 Maths Chapter 6 Perimeter And Area — SparkEd

Chapter 6 Overview: Perimeter and Area

Chapter 6 of the NCERT Class 6 Maths textbook (2024-25) introduces two fundamental measurements in geometry — perimeter (the distance around a shape) and area (the space inside a shape).

The key topics covered are:
- Perimeter — the total length of the boundary of a figure
- Area — the amount of surface enclosed by a figure
- Perimeter and area of rectangles and squares — using standard formulas
- Area of triangles — half of base times height
- Composite figures — combining and subtracting areas
- Unit conversions — relating cm, m, km and their squared versions

These concepts have direct real-world applications: fencing a garden (perimeter), tiling a floor (area), and many more.

Exercise 6.1 — Perimeter

This exercise focuses on computing the perimeter of various shapes.

Problem: Perimeter of a rectangle

Question: Find the perimeter of a rectangle with length 1212 cm and breadth 88 cm.

Solution:

Perimeter of a rectangle:

P=2×(length+breadth)P = 2 \times (\text{length} + \text{breadth})

P=2×(12+8)P = 2 \times (12 + 8)

P=2×20=40 cmP = 2 \times 20 = 40 \text{ cm}

Answer: The perimeter is 4040 cm.

Problem: Perimeter of a square

Question: A square park has a side of 5050 m. Find the total distance covered if a person walks around it 33 times.

Solution:

Perimeter of a square:

P=4×side=4×50=200 mP = 4 \times \text{side} = 4 \times 50 = 200 \text{ m}

Distance for 33 rounds:

Total distance=3×200=600 m\text{Total distance} = 3 \times 200 = 600 \text{ m}

Answer: The person covers 600600 m.

Problem: Finding a missing side from perimeter

Question: The perimeter of a rectangle is 5656 cm and its length is 1818 cm. Find its breadth.

Solution:

P=2(l+b)P = 2(l + b)

56=2(18+b)56 = 2(18 + b)

28=18+b28 = 18 + b

b=2818=10 cmb = 28 - 18 = 10 \text{ cm}

Answer: The breadth is 1010 cm.

Verification: P=2(18+10)=2×28=56P = 2(18 + 10) = 2 \times 28 = 56 cm ✓

Problem: Perimeter of a triangle

Question: Find the perimeter of a triangle with sides 77 cm, 99 cm, and 1111 cm.

Solution:

Perimeter of a triangle = sum of all three sides.

P=7+9+11=27 cmP = 7 + 9 + 11 = 27 \text{ cm}

Answer: The perimeter is 2727 cm.

For an equilateral triangle (all sides equal) with side aa: P=3aP = 3a.

Exercise 6.2 — Area of Rectangles and Squares

This exercise covers computing the area of rectangles and squares.

Problem: Area of a rectangle

Question: Find the area of a rectangle with length 1515 cm and breadth 99 cm.

Solution:

A=length×breadthA = \text{length} \times \text{breadth}

A=15×9=135 cm2A = 15 \times 9 = 135 \text{ cm}^2

Answer: The area is 135135 cm2^2.

The unit of area is always a squared unit (cm2^2, m2^2, km2^2) because area measures two-dimensional space.

Problem: Area of a square

Question: A square tile has a side of 2020 cm. Find its area. How many tiles are needed to cover a floor of area 22 m2^2?

Solution:

Area of one tile:

A=side2=202=400 cm2A = \text{side}^2 = 20^2 = 400 \text{ cm}^2

Convert 22 m2^2 to cm2^2:

2 m2=2×10000 cm2=20000 cm22 \text{ m}^2 = 2 \times 10000 \text{ cm}^2 = 20000 \text{ cm}^2

Number of tiles:

20000400=50\frac{20000}{400} = 50

Answer: The area of each tile is 400400 cm2^2, and 5050 tiles are needed.

Unit conversion reminder: 11 m =100= 100 cm, so 11 m2=100×100=10000^2 = 100 \times 100 = 10000 cm2^2.

Problem: Finding a side from the area

Question: The area of a rectangular garden is 480480 m2^2 and its length is 2424 m. Find its breadth and perimeter.

Solution:

Breadth:

A=l×bA = l \times b

480=24×b480 = 24 \times b

b=48024=20 mb = \frac{480}{24} = 20 \text{ m}

Perimeter:

P=2(l+b)=2(24+20)=2×44=88 mP = 2(l + b) = 2(24 + 20) = 2 \times 44 = 88 \text{ m}

Answer: Breadth =20= 20 m, Perimeter =88= 88 m.

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Exercise 6.3 — Area of Triangles and Composite Figures

This exercise extends area calculations to triangles and combined shapes.

Problem: Area of a triangle

Question: Find the area of a triangle with base 1414 cm and height 1010 cm.

Solution:

A=12×base×heightA = \frac{1}{2} \times \text{base} \times \text{height}

A=12×14×10=1402=70 cm2A = \frac{1}{2} \times 14 \times 10 = \frac{140}{2} = 70 \text{ cm}^2

Answer: The area is 7070 cm2^2.

Why is it half? A triangle is exactly half of a parallelogram (or rectangle) with the same base and height.

Problem: Area of a composite figure

Question: An L-shaped room has the following dimensions: the overall shape is 1010 m by 88 m, with a 44 m by 33 m rectangular portion cut out from one corner. Find the area of the room.

Solution:

Method: Subtract the cut-out from the full rectangle.

Area of full rectangle:

A1=10×8=80 m2A_1 = 10 \times 8 = 80 \text{ m}^2

Area of cut-out:

A2=4×3=12 m2A_2 = 4 \times 3 = 12 \text{ m}^2

Area of L-shaped room:

A=A1A2=8012=68 m2A = A_1 - A_2 = 80 - 12 = 68 \text{ m}^2

Answer: The area of the room is 6868 m2^2.

Strategy for composite figures: Either split the shape into simpler shapes and add their areas, or start with a larger shape and subtract the missing parts.

Problem: Same perimeter, different areas

Question: Two rectangles both have a perimeter of 2424 cm. One is 88 cm by 44 cm, the other is 77 cm by 55 cm. Which has a greater area?

Solution:

Rectangle 1: l=8l = 8 cm, b=4b = 4 cm

P=2(8+4)=24 cmP = 2(8 + 4) = 24 \text{ cm}

A1=8×4=32 cm2A_1 = 8 \times 4 = 32 \text{ cm}^2

Rectangle 2: l=7l = 7 cm, b=5b = 5 cm

P=2(7+5)=24 cmP = 2(7 + 5) = 24 \text{ cm}

A2=7×5=35 cm2A_2 = 7 \times 5 = 35 \text{ cm}^2

Answer: The second rectangle (7×57 \times 5) has a greater area (3535 cm2^2 vs 3232 cm2^2), even though both have the same perimeter.

Key insight: Among all rectangles with a given perimeter, the square has the largest area. As the shape becomes more "square-like," the area increases.

Key Concepts and Formulas

Here is a summary of all formulas from Chapter 6.

Perimeter formulas:
- Rectangle: P=2(l+b)P = 2(l + b)
- Square: P=4sP = 4s
- Triangle: P=a+b+cP = a + b + c (sum of all sides)
- Equilateral triangle: P=3aP = 3a

Area formulas:
- Rectangle: A=l×bA = l \times b
- Square: A=s2A = s^2
- Triangle: A=12×b×hA = \frac{1}{2} \times b \times h

Unit conversions:
- 11 m =100= 100 cm
- 11 km =1000= 1000 m
- 11 m2=10,000^2 = 10{,}000 cm2^2
- 11 km2=1,000,000^2 = 1{,}000{,}000 m2^2

Key relationship: Shapes with the same perimeter can have different areas. Among rectangles with a fixed perimeter, the square has the maximum area.

Tips for Solving Perimeter and Area Problems

1. Identify what is asked. Read carefully — perimeter is a length (cm, m), area is a squared unit (cm2^2, m2^2). Mixing them up is a common error.

2. Draw and label. Always sketch the figure and mark all given dimensions.

3. For composite figures, either break the shape into rectangles/triangles and add, or subtract from a larger shape.

4. Check units. Make sure all measurements are in the same unit before calculating. Convert if necessary.

5. Verify your answer. After finding a missing dimension, plug it back in to check the original condition (perimeter or area).

Practice on SparkEd

Perimeter and Area problems appear in every grade and in competitive exams. SparkEd has 60 practice questions on Perimeter & Area for Class 6 CBSE, with detailed step-by-step solutions.

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