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

Its very simple

small balloon's radius (r)=7cm
big balloon's Radius (R)=14 cm
so ,
the ratio= (4*pi*r^2)/(4*pi*R^2)
= r^2/R^2
= 7^2/14^2
= 49/196
= 1/4
= 1:4 ans

Answer 2

total surface area of first spherical balloon=2 pi r²  =   2 pi 7*7
total surface area of second spherical balloon=2 pi r² = 2 pi 14*14
ratio of surface area=2 pi 7*7   
                             2 pi 14*14
that is  1 
         2*2
=1:4