The total circumference of two circles is 25. If the first circle has a circumference that is exactly twice the circumference of the second circle, then what is the approximate sum of their two radii?
Select.
A) 5.7  B) 6.0  C) 4.0  D) 9.7  E) 18.0

Rationale: "let r = radius of smaller circle . let r = radius of larger circle therefore : 2 π r + 2 π r = 25 where 2 r = r thus : 2 π r + 4 π r = 25 6 π r = 25 r = approx 1.33 π r + 2 r π = 25 3 π r = 25 r = approx 2.65 r + r = approx 3.98 = 4.0 answer : c"
Answer: C