At what rate percent per annum will a sum of money double in 7 years.	Choose the most appropriate option
A) 12.5 %  B) 13.5 %  C) 14.2 %  D) 14.5 %  E) 21.5 %

Rationale: "let principal = p , then , s . i . = p and time = 8 years rate = [ ( 100 x p ) / ( p x 8 ) ] % = 14.2 % per annum . answer : c"
Answer: C