The simple interest and the true discount on a certain sum and at a given rate are Rs.25 and Rs.20 respectively. The sum is

Explanation:

Let that amount be Rs.x and rate is r%.Then, for simple interestx×r/100=25=> x×r=2500 … … (i)For true discount(x−20)×r/\100=20x×r−20r\100=20=> xr – 20r = 2000 … … (ii)From Eqs. (i) and (ii), we get2500 – 20r = 2000=> r = 25%From Eq. (i)x×258 = 2500=> x = Rs.100