A sum of money at simple interest amounts to Rs. 815 in 3 years and to Rs. 854 in 4 years. The sum is?
Answer: C
S.I. for 1 year = (854 - 815) = Rs. 39
S.I. for 3 years = 39 * 3 = Rs. 117
Principal = (815 - 117) = Rs. 698.