the rate at which a sum becomes 4 times of itself in 15 years at s . i . , will be :	Pick: A) 10 % B) 15 % C) 20 % D) 40 % E) none

Rationale: sol . let sum = x . then , s . i . = 3 x ∴ rate = [ 100 * s . i . / p * t ] = [ 100 * 3 x / x * 15 ] % = 20 % . answer c
Answer: C