A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 860 in 4 years. The sum is: Choose the correct choice from the following answers.
A) s. 650  B) s. 690  C) s. 680  D) s. 700  E) s. 720
S.I. for 1 year = Rs. (860 - 815) = Rs. 45.   S.I. for 3 years = Rs.(45 x 3) = Rs. 135.   Principal = Rs. (815 - 135) = Rs. 680.   Answer: Option s. 680
<result>C</result>
A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 860 in 4 years. The sum is: