A Certain sum of money amounts to Rs 2500 in a span of 5 years and further to Rs.3000 in a span of 7 years at simple interest. The sum is ?

As the rate of interest for both the cases are same
A1, A2 = Total Amounts , P = Principal Amount , T1, T2 = Time Period involved in years
(A1 – P) / T1 = (A2 – P) / T2
(2500 – P) / 5 = (3000 – P) / 7
17500 – 7P = 15000 – 5P
P = 1250