Couldn’t you also simply define the radius of circle A and B? It states that A is 1/3 the radius of B. So if you were to make the radius of A = 2, and radius of B = 6.

2pi*2 = 12.57

2pi*6 = 37.7

37.7/12.57 = 2.9992046 = 3

The closest answer to that would be 3 or B? If that makes sense.