If the radius of circle B is 5 times the radius of circle A, then the ratio of the area of circle B to that of circle A is:
A) 25
B) 5
C) 0.2
D) 0.04
E) 0.025

Question

Quizplus · Accepted Answer

Let's assume the radius of circle A is "r". 
Then, radius of circle B will be 5r. 
Area of circle A = πr²
Area of circle B = π(5r)² = 25πr²
So, the ratio of the area of circle B to that of circle A = 25πr²/πr² = 25.

If the Radius of Circle B Is 5 Times the Radius