the rate at which a sum becomes 4 times of itself in 15 years at s . i . , will be :
sol . let sum = x . then , s . i . = 3 x ∴ rate = [ 100 * s . i . / p * t ] = [ 100 * 3 x / x * 15 ] % = 20 % . answer c
divide(multiply(const_3, const_100), 15)