If a sum of money doubles itself in 25 years at simple interest, the ratepercent per annum is Pick
A) 12
B) 12.5
C) 13
D) 13.5
E) 4
4xplanation:   Let sum = x then Simple Interest = x   Rate = (100 * x) / (x * 25) = 4   Option 4
<result>E</result>
If a sum of money doubles itself in 25 years at simple interest, the ratepercent per annum is