An amount at compound interest sums to Rs.17640/- in 2 years and to Rs.21168/- in 3 years at the same rate of interest. Find the rate percentage?	Select:
A) 5%	B) 7%	C) 9%	D) 11%	E) 20%
Explanation:   The difference of two successive amounts must be the simple interest in 1 year on the lower amount of money.   S.I = 21168/- - 17640/- = Rs. 3528/-   Rate of interest = (3528/17640) × (100/1) =&gt; 20%   Answer: Option 20%
<result>E</result>
An amount at compound interest sums to Rs.17640/- in 2 years and to Rs.21168/- in 3 years at the same rate of interest. Find the rate percentage?