As air is pumped into a spherical balloon, its radius increases from 7 cm to 14 cm. Find the ratio of volume of the balloon's in both circumstances.

1 : 8

Let, r = radius before pumping and,

 R = radius after pumping air.

We know that,

= volume : VOLUME = r³ : R³

We have,

 r : R = 7 : 14 = 1 : 2

According to the concept,

= v : V = r³ : R³ = 7³ : 14³

= 1³ : 2³ = 1 : 8