We know that simple interest (S.I.) S.I. = (P.r.t)/100, Where P = principal, r = rate and t = time. So, total debt discharged = (amount discharged in 1st year) + (amount discharged in 2nd year) + (amount discharged in 3rd year) + (amount discharged in 4th year) + (amount discharged in 5th year) i.e Total debt discharged = P + (P + Pr/100) + (P + 2Pr/100) + (P + 3Pr/100) + (P + 4Pr/100) Putting, total debt discharged = 6000 and r = 10% we get 6000 = 6P ⇒ P = Rs. 1000