At what rate percent of simple interest will a sum of money double itself in 12 years?
Choices:
A) 8 1/7 %  B) 8 1/3 %  C) 8 7/3 %  D) 6 1/3 %  E) 8 9/3 %
Let sum = x. Then, S.I. = x.   Rate = (100 * S.I.) / (P * T) = (100 * x) / (x * 12)   = 25/3 = 8 1/3 %   Answer: 8 1/3 %
<result>B</result>
At what rate percent of simple interest will a sum of money double itself in 12 years?