If a sum of money doubles itself in 15 years at simple interest, the ratepercent per annum is	Choose one.
A) 12
B) 12.5
C) 6.67
D) 13.5
E) 14
Explanation:   Let sum = x then Simple Interest = x   Rate = (100 * x) / (x * 15) = 6.67   Option 6.67
<result>C</result>
If a sum of money doubles itself in 15 years at simple interest, the ratepercent per annum is