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?  Choose the most appropriate option
A) 7
B) 6
C) 5
D) 4
E) 2
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?