If the radius of a sphere is increased by 30%, by what percentage does its surface area increase?
Show answer & explanation
Correct answer: C
Explanation
Increase in radius = 30%
Surface area = r²
New radius = 1.3r
New area = (1.3)² = 1.69
Increase = 1.69 − 1 = 0.69
Percentage increase = 0.69 × 100 = 69%