The radius of a sphere is $14 \, cm$. Find its surface area (in $cm^2$).

$A$ hemispherical metallic bowl is made of steel,$0.2 \, cm$ thick. The inner radius of the bowl is $4 \, cm$. Find the outer curved surface area of the bowl (in $cm^2$).

Find the radius of a sphere whose surface area is $154 \, cm^2$. (in $, cm$)

The radius of a sphere is decreased by $20 \% .$ By what per cent does its curved surface area decrease (in $\%$)?

Find the surface area of a sphere with a diameter of $3.5 \, cm$. Assume $\pi = \frac{22}{7}$. (in $, cm^2$)

Surface area of a sphere $= \ldots \ldots.$