Question

john borrowed some money from bank at 12.5 percent per annum simple interest and lent the entire amount to mary on the same date at 18 percent per annum. thus after 3 years ,he gained 792 rupees. find the sum.

Answer 1

let the principle (sum borrowed) be x
interest john had to pay to the bank =
= 12.5*3*x/100
interest mary had to pay = 18*3*x/100
profit of john = rs.729
money gained = interest he got - interest he paid
729 = 0.54x - 0.375x
729 = 0.165x
x = 4418
therefore sum= rs.4418