If the radius of a hemispherical balloon increases from 4 cm to 7 cm as air is pumped into it, find the ratio of the surface area of the new balloon to its original.
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 49 : 16.
Given that
If the radius of a hemispherical balloon increases from 4 cm to 7 cm
The surface area of a hemisphere = 3πr2
The ratio of the surface area of the new balloon to its original = (3π × 72)/(3π × 42) = 49/16
Hence, the required ratio = 49 : 16