1 year ago
Last edited at 9:40AM on 3/10/2013
The radius of circle B is 26. To get this, we first assume the area of circle A is y, and that of circle B is 4y. Since the area of a circle is ?r^2, we have the area of circle A as 3.14 * 13 *13, which is 530.66 m^2. The area of circle B is (530.66 * 4), which is 2122.64m^2. To find the radius of circle B, we divide 2122.64 by 3.14 to get 676. The square root of 676 is 26.
Area of a circle = (pi)(radius^2). Using that formula, you can find the area of circle A. Then multiply that number by 4 to find the area of circle B. Finally, divide THAT number by pi to find its radius^2, and then square-root that number to find its radius. . Or, perhaps an easier way to figure this out, is you could find out what 13^2 is, multiply THAT number by 4, and then find the square root of that number. I think that both methods would end up giving you the same answer, however the second one appears to be much simpler..
Circles are always similar, so you can jump from the first dimension( radius ratio) to the second dimension(area ratio) this way: (R/R)^2=A/A. Or (R/R)= sqrt(A/A) Since you know the area/area ratio is 1/4, then sqrt that (1/2) and you'll know the r/r ratio. 1/2=13/x. X=26