GIVEN: Rate of interest is 6% per annum for the first 2 years, 8% per annum for the next 2 years and 10% per annum for the last 2 years. Principal = Rs. 40000 CONCEPT: Simple interest concept. Cumulative rate if the rate of interest is ‘ R1 ’ for ‘ T1 ’ years and ‘ R2 ’ for ‘ T2 ’ years = R1T1+R2T2 FORMULA USED: SI = PRT/100 Where P = Principal, R = rate of interest, T = Time CALCULATION: Cumulative rate = 6×2+8×2+10×2=48% Principal = Rs. 40000 So, SI = [40000 × 48]/100 ⇒ SI = 19200 Hence, Total interest earned = Rs. 19200