Given: Time = 3 years Rate of interest = 5% S.I = Rs. 180 Formula used: S.I = PRT/100 Where, P = Principal R = Rate of interest T = Time Calculation: Rs. 180 = (P × 5 × 3)/100 ⇒ Rs. 180 = 15P/100 ⇒ Rs. 12 × 100 = P ⇒ Rs. 1200 = P ∴ The principal amount is Rs. 1200