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

Solution:

Let the radius of the sphere be r.

Surface area of sphere = 154

$\therefore 4 m r^{2}=154 \mathrm{~cm}^{2}$

$r^{2}=\left(\frac{154 \times 7}{4 \times 22}\right) \mathrm{cm}^{2}=\left(\frac{7 \times 7}{2 \times 2}\right) \mathrm{cm}^{2}$

$r=\left(\frac{7}{2}\right) \mathrm{cm}=3.5 \mathrm{~cm}$

Therefore, the radius of the sphere whose surface area is $154 \mathrm{~cm}^{2}$ is $3.5 \mathrm{~cm}$.