) 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
Explanation: We know that the total surface area of the hemisphere = 3πr2 square units.