A sum of money invested at C.I. amounts to Rs. 800 in 3 years to Rs. 840 in 4 years. The rate of interest per annum is?  Pick one: A) 2 1/2 % B) 4% C) 5% D) 6 2/3 % E) 6%
S.I. on Rs. 800 for 1 year = (840 - 800) = Rs. 40 Rate = (100 * 40)/(800 * 1)= 
<gadget id="calculator">(100 * 40)/(800 * 1)</gadget>
<output>5</output>
5%   ANSWER:5%
<result>C</result>
A sum of money invested at C.I. amounts to Rs. 800 in 3 years to Rs. 840 in 4 years. The rate of interest per annum is?