Question

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

Answer 1

surface area of small balloon : surface area of large ballon
$4 \pi r^2 : 4 \pi R^2$
therefore [tex]=r^2 : R^2 =7^2 : 14^2 =49 : 196[/tex]
=1 : 4

Answer 2

surface area of small balloon=4πr^2
4*22/7*7^2=616cm^2
surface area of large balloon=4πr^2
4*22/7*14^2=2464cm^2