MAT Exam 2022 Paper

Concept:In simple interest, the interest earned each year is constant. Therefore, comparing the amounts at two time points gives the yearly interest directly.Explanation:Amount after 3 years $= ₹300$.Amount after another 5 years, that is after 8 years $= ₹400$.Interest earned in these 5 extra years $= 400 - 300 = ₹100$.Interest earned in 1 year $= \frac{100}{5} = ₹20$.Interest earned in 3 years $= 3 \times 20 = ₹60$.Principal $= \text{Amount after 3 years} - \text{Interest for 3 years}$.So, Principal $= 300 - 60 = ₹240$.Rate of interest $= \frac{\text{Interest per year}}{\text{Principal}} \times 100$.Rate of interest $= \frac{20}{240} \times 100 = 8.33\%$.Answer:The rate of interest is $8.33\%$, which corresponds to option D.