The ratio of surface areas of 2 cubes is 1 : 9. Find the ratio of their volumes.

Let the side of one cube is 2 cmThen surface area = 6 l2 = 6 x 2 x 2 = 24 cm2  Other cube's surface area will be 9 x 24 = 216 cm2

( as they are in ratio of 1: 9 ) 

now      6 l2 = 216              l2 = 216 / 6

               l2 = 36               l = 6volume of first cube  = side x side x side                                      = 2 x 2 x 2 = 8 cm3                                      volume of other cube = 6 x 6 x 6  = 216 cm3              Ratio = 8 / 216 = 1 / 27

       so ratio will be 1 : 27