A circular carpet of diameter $1.4 m$ is stopped in the centre with a $20 c m$ striped border. Find the area of the striped portion of the carpet in the nearest $c m^{2}$ .

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Solution

Let $1.4 m = 140 c m$
Radius $= \frac{140}{2} = 70 c m$
Extra strip is of diameter
$= 20 c m / 2$ .
Radius $= 10 c m$
$∴$ Radius for outer circle
$= 80 c m$
Area of that path or strip
$= \frac{22}{7} \times R^{2} - \frac{22}{7} \times r^{2}$
$= \frac{22}{7} (R^{2} - r^{2})$
$= \frac{22}{7} (80 + 70) (80 - 70)$
$= \frac{22}{7} \times 150 c m \times 10 c m$
$= \frac{33000}{7} c m^{2}$

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A circular carpet of diameter 1.4 m is stopped in the centre with a 20 cm striped border. Find the area of the striped portion of the carpet in the nearest cm2.

Let 1.4 m=140 cmRadius =1402=70 cmExtra strip is of diameter =20 cm/2.Radius =10 cm∴ Radius for outer circle =80 cmArea of that path or strip =227×R2−227×r2=227(R2−r2)=227(80+70)(80−70)=227×150 cm×10 cm=330007 cm2

A circular carpet of diameter $1.4 m$ is stopped in the centre with a $20 c m$ striped border. Find the area of the striped portion of the carpet in the nearest $c m^{2}$ .