A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 878 in 4 years. The sum is:  Choose the correct choice from the following answers:
A) 500	B) 698	C) 626	D) 910	E) None
Sol.   S.I. for 1 year = Rs. (878 - 815) = Rs. 63.   S.I. for 3 years = Rs. (63 * 3) = Rs. 189.   âˆ´ Principal = Rs. (815 - 189) = Rs. 626   Answer 626
<result>C</result>
A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 878 in 4 years. The sum is: