GIVEN: P = Rs. 15000, A = Rs. 18600, T = 4 years FORMULA USED: Simple Interest = PRT/100 Where, P = principle, R = Rate of interest, T = time period CALCULATION: SI = 18600 - 15000 = Rs. 3600 ⇒3600=(15000×4×R)/100 ⇒R=360000/60000=6 ∴ Rate of interest is 6%