If ₹ 64 amounts to ₹ 83.20 in 2 years, what will ₹ 86 amount to in 4 years at the same rate percent per annum?

Correct answer: ₹ 137.60

Explanation: ✅ Correct Answer: D) ₹ 137.60 📚 Explanation: Step 1: Find the interest earned on ₹ 64 in 2 years: $\text{Interest} = 83.20 - 64 = ₹ 19.20$. Use the simple interest formula to calculate the annual rate ($R$): $$19.20 = \frac{64 \times R \times 2}{100} \implies 128R = 1920 \implies R = 15\%$$ Step 2: Apply the same rate of 15% to calculate the interest earned on ₹ 86 over a period of 4 years: $$\text{New Interest} = \frac{86 \times 15 \times 4}{100} = \frac{86 \times 60}{100} = ₹ 51.60$$ Step 3: Calculate the final total amount by adding this new interest to the principal: $$\text{Total Amount} = 86 + 51.60 = ₹ 137.60$$