an amount at compound interest sums to rs. 17640 / - in 2 years and to rs. 20286 / - in 3 years at the same rate of interest. find the rate percentage?
Answers:  A) 5 %  B) 7 %  C) 9 %  D) 15 %  E) 12 %
<gadget id="calculator">20_286 - 17_640</gadget>
<output>2_646</output>

<gadget id="calculator">2_646 / 17_640</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(3/20) * 100</gadget>
<output>15</output>

<result>D</result>
an amount at compound interest sums to rs. 17640 / - in 2 years and to rs. 20286 / - in 3 years at the same rate of interest. find the rate percentage?
multiply(divide(subtract(20286, 17640), 17640), const_100)
"explanation : the difference of two successive amounts must be the simple interest in 1 year on the lower amount of money . s . i = 20286 / - - 17640 / - = rs . 2646 / - rate of interest = ( 2646 / 17640 ) × ( 100 / 1 ) = > 15 % answer : option d"