CLASS 7 MATHS · PERIMETER AND AREA

Circumference and area of a circle

Circumference = 2πr, area = πr². Take π = 22/7.

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Worked examples

Example 1 · level 1

A circular clock face has radius 14 cm. Find its circumference (in cm). Use π = 22/7.

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Circumference = 2 × 22/7 × 14 = 88 cm.

Answer: 88

Example 2 · level 2

A circular chapati tawa has diameter 70 cm. Find its circumference (in cm). Use π = 22/7.

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r = 70 ÷ 2 = 35 cm.
Circumference = 2 × 22/7 × 35 = 220 cm.

Answer: 220

Example 3 · level 3

A circular flower bed of radius 7 m in a Lucknow park has a path around it, so the outer radius is 21 m. Find the area of the path (in m²). Use π = 22/7.

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Area = 22/7 × (21² − 7²) = 22/7 × 392
= 1,232 m².

Answer: 1,232