The total circumference of two circles is 80. 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?	Choose the correct answer.
A) 5.7
B) 6.0
C) 10.6
D) 9.7
E) 18.0
Let r= Radius of smaller circle. Let R = Radius of larger circle   Therefore:   2πr + 2πR = 80   where 2r = R   Thus:   2πr + 4πr = 80   6πr = 80   r = approx 4.2   πR + 2Rπ = 80   3πR = 80   R = approx 8.4   r + R = approx 10.6   Answer is 10.6
<result>C</result>
The total circumference of two circles is 80. 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?