Find the surface area of a sphere of diameter $49\, cm$ (in $cm^2$).

The hollow sphere,in which the circus motorcyclist performs his stunts,has a diameter of $7 \,m$. Find the area available to the motorcyclist for riding. (in $,m^2$)

Find the surface area of a sphere of radius $14 \, cm$.
Assume $\pi = \frac{22}{7}$. (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 $cm^2$).

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

The surface area of a sphere and the curved surface area of a hemisphere are equal. Find the ratio of their radii.