Given: Time = 4 years Rate = 12.5% Formula used: Amount = Simple interest + Principal SI=(PxRxT)/100 where P = Principal, R = Rate of Interest, T = Time Period of the Loan/deposit in years, SI = Simple Interest Calculations: Let, the principal is P SI=(PxRxT)/100 ⇒P−400=(P×4×12.5)/100 ⇒P−400=P×4×(1/8) ⇒P−400=P/2 ⇒2P−800=P ⇒P=800Rs. ∴ The sum is 800 Rs.