急..Mensuration

Ratio of radius of container A : container B = 1 : 2
So, the ratio of surface area of container A : container B = 1² : 2² = 1 : 4

The cost of painting the outer surface of container A is $80,
the cost of painting for the outer surface of container B will be $80 * 4
= $320

2007-02-25 21:04:55 補充：
answer is $720?IF the radius of container B is 3 TIMES (instead of 2 times) that of container A,the answer will be $720.Isn't it?