Ex.11.3 Q2 Perimeter and Area - NCERT Maths Class 7

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Find the area of the following circles, given that:\(\begin{align}\left( {{\rm{Take\, }}\pi = \frac{{22}}{7}} \right)\end{align}\)

(a) Radius \(= 14\,\rm mm\)

(b) Diameter \(= 49 \,\rm m\) 

(c) Radius \(= 5 \,\rm cm\)

 Video Solution
Perimeter And Area
Ex 11.3 | Question 2

Text Solution

What is known?

Radius or diameter of the circles.

What is unknown?

The Area of the circles.


In this question, radius (or diameter) of the circle is given. Put the value of the radius in the formula of area of the circle to find out the area.


(a) Given,

Radius of the circle \(= 14 \,\rm mm\)

Area of circle

\[\begin{align}&= \pi {r^2}\\&= \frac{{22}}{7} \times 14 \times 14\\&= 22 \times 2 \times 14\\&= 616\;\rm m{m^2}\end{align}\]

(b) Given,

Diameter of the circle \(= 49 \,\rm m\)

Therefore, radius \(= 24.5 \,\rm m\)

Area of circle

\[\begin{align}&= \pi {r^2}\\&= \frac{{22}}{7} \times 24.5 \times 24.5\\&= 22 \times 24.5 \times 3.5\\&= 1886.5\;\rm {m^2}\end{align}\]

(c) Given,

Radius of the circle \(= 5 \,\rm cm\)

Area of circle

\[\begin{align}&= \pi {r^2}\\&= \frac{{22}}{7} \times 5 \times 5\\ &= \frac{{550}}{7}\\&= 78.57\;\rm c{m^2}\end{align}\]