At what rate percent per annum will a sum of money double in 9 years.  Choose the correct choice from the following
A) 12.5 %	B) 13.5 %	C) 11.5 %	D) 11.1 %	E) 21.5 %

Rationale: "let principal = p , then , s . i . = p and time = 8 years rate = [ ( 100 x p ) / ( p x 9 ) ] % = 11.1 % per annum . answer : d"
Answer: D