The radius of a hemispherical balloon increases from 6 cm to 12 cm as air is being pumped into it. The ratio of the surface areas of the balloon in the two cases is :
A. 1:4
B. 1:3
C. 2 : 3
D. 2 : 1
Answer:A
The radius of a hemispherical balloon increases from 6 cm to 12 cm as air is being pumped into it. The ratio of the surface areas of the balloon in the two cases is :
A. 1:4 B. 1:3 C. 2 : 3 D. 2 : 1