An amount at compound interest sums to Rs.17640/- in 2 years and to Rs.22932/- 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) 11 %	E) 30 %

Rationale: "explanation : the difference of two successive amounts must be the simple interest in 1 year on the lower amount of money . s . i = 22932 / - - 17640 / - = rs . 5292 / - rate of interest = ( 5292 / 22932 ) × ( 100 / 1 ) = > 30 % answer : option e"
Answer: E