Ex.11.3 Q1 Perimeter and Area - NCERT Maths Class 7

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Find the circumference of the circles with the following radius:

\(\begin{align}\left( {{\rm{Take}}\;\pi = \frac{{22}}{7}} \right)\end{align}\)

(a) \(14 \,\rm cm\)   

(b) \(28 \,\rm mm \)    

(c) \(21 \,\rm cm\)

 Video Solution
Perimeter And Area
Ex 11.3 | Question 1

Text Solution

What is known?

Radius of the circle

What is unknown?

The circumference of the circles.


In this question, radius of the circle is given. Put the value of the radius in the formula of circumference of the circle to find out the circumference.


(a) Circumference of the circle

\[\begin{align} &= 2\pi r\\&= 2 \times \frac{{22}}{7} \times 14\\&= 2 \times 22 \times 2\\&= 88\;\rm{cm}\end{align}\]

(b) Circumference of the circle

\[\begin{align}&= 2\pi r\\&= 2 \times \frac{{22}}{7} \times 28\\&= 2 \times 22 \times 4\\&= 176\;\rm{mm}\end{align}\]

(c) Circumference of the circle

\[\begin{align}&= 2\pi r\\&= 2 \times \frac{{22}}{7} \times 21\\&= 2 \times 22 \times 3\\&= 132\;\rm{cm}\end{align}\]