An amount at compound interest sums to Rs.17640/- in 2 years and to Rs.22050/- in 3 years at the same rate of interest. Find the rate percentage?  Select the correct option:
A) 5 %
B) 7 %
C) 9 %
D) 11 %
E) 25 %

Rationale: "explanation : the difference of two successive amounts must be the simple interest in 1 year on the lower amount of money . s . i = 22050 / - - 17640 / - = rs . 4410 / - rate of interest = ( 4410 / 17640 ) × ( 100 / 1 ) = > 25 % answer : option e"
Answer: E