Find the radius of a sphere whose surface area is $ 154 \mathrm{~cm}^{2} $.

AcademicMathematicsNCERTClass 9

Given: 

The surface area of a sphere is $154\ cm^{2}$.

To do: 

We have to find the radius of the sphere.

Solution:

Let $r$ be the radius of the sphere.

Therefore,

Surface area of the sphere$=4\pi r^2$

$=154$

This implies,

$r^2=\frac{154}{4\pi}$

$r^2=\frac{154}{4\times\frac{22}{7}}$

$r^2=\frac{154\times7}{4\times22}$

$r^2=\frac{49}{4}$

$r^2=\frac{7^2}{2^2}$

$r=\frac{7}{2}$

$r=3.5\ cm$

Therefore, the radius of the sphere is $3.5\ cm$.

raja
Updated on 10-Oct-2022 13:46:37

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