Question 338188
If the diameter of circle A is twice as large as the diameter of circle B, what is the ratio of the area of the larger circle to the area of the smaller circle? 
(a) 8: 1 (b) 6:1 (c) 4: 1 (d) 2: 1 (e) 3: 2



area = pi * r^2, r = radius = diameter/2, d = diameter
area = pi * (d/2)^2 = pi * (d^2)/4   (d/2 * d/2 = (d^2)/4)
circle B --> pi * (d^2)/4
circle A (twice as large) --> pi * (2d * 2d)/4 --> pi * (4d^2)/4 --> pi * d^2
ratio circle A area to circle B area --> (d^2)/((d^2)/4)


d^2 * 4/(d^2) = 4


ratio is 4 to 1, so answer is (c) 4:1