A sum of money invested at compound interest amounts to Rs.800 in 3 years and to Rs.840 in 4 years. The rate of interest per annum is
Select.
A) 2x1/2%
B) 4%
C) 5%
D) 6x2/3%
E) None
Solution   S.I. on Rs.800 for 1 year	=Rs[840 - 800]   = Rs.40   Rate	=(100x40/800x1)%   = 5%   Answer 5%
<result>C</result>
A sum of money invested at compound interest amounts to Rs.800 in 3 years and to Rs.840 in 4 years. The rate of interest per annum is