A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 864 in 4 years. The sum is: Select the correct option
A) s. 650  B) s. 690  C) s. 668  D) s. 700  E) s. 760
S.I. for 1 year = Rs. (864 - 815) = Rs. 49.   S.I. for 3 years = Rs.(49 x 3) = Rs. 147.   Principal = Rs. (815 - 147) = Rs. 668.   Answer: Option s. 668
<result>C</result>
A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 864 in 4 years. The sum is: