The rate at which a sum becomes four times of itself in 15 years at S.I., will be : Pick:	A) 10 %	B) 15 %	C) 20 %	D) 40 %	E) None
Sol.   Let sum = x. Then, S.I. = 3x   ∴ Rate = [100 * S.I. / P*T] = [100 * 3x / x * 15]% = 20%.   Answer 20 %
<result>C</result>
The rate at which a sum becomes four times of itself in 15 years at S.I., will be :