An amount at compound interest sums to Rs.17640/- in 2 years and to Rs.19404/- in 3 years at the same rate of interest. Find the rate percentage? Choose the correct choice from the following answers:
A) 5 %
B) 7 %
C) 9 %
D) 10 %
E) 12 %

Rationale: explanation : the difference of two successive amounts must be the simple interest in 1 year on the lower amount of money . s . i = 19404 / - - 17640 / - = rs . 1764 / - rate of interest = ( 1764 / 17640 ) × ( 100 / 1 ) = > 10 % answer : option d
Answer: D