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# The radius of a spherical balloon increases from 7 cm to 14 cm as air is being pumped into it. Find the ratio of surface areas of the balloon in the two cases.

Given :
Radius (r) of spherical balloon = 7 cm
Radius (R) of spherical balloon, when air is pumped into it = 14 cm

= $$\frac{Initial surface area}{Surface area after pumping air into balloon}$$
= $$[\frac{4 × {\pi} × {r}^2}{4 × {\pi} × {R}^2}]$$ $$= (\frac{r}{R})^2$$
= $$(\frac{7}{14})^2 = \frac{1}{4}$$

Therefore, the ratio between the surface areas in these two cases is 1 : 4.