Explanation:

To determine the time required for Rs.3,720 to amount to Rs.5,282.4 with an interest rate of 12% simple interest per annum, follow these steps:

- Formula for Simple Interest:

$$ \text{Simple Interest (SI)} = \frac{\text{Principal (P)} \times \text{Rate (R)} \times \text{Time (T)}}{100} $$

- Calculate Simple Interest:

$$ \text{SI} = \text{Amount} - \text{Principal} = 5,282.4 - 3,720 = 1,562.4 $$

- Use the Simple Interest Formula:

- $$ 1,562.4 = \frac{3,720 \times 12 \times T}{100} $$

- Solve for T:

- $$ 1,562.4 = 446.4 \times T $$

- $$ T = \frac{1,562.4}{446.4} \approx 3.5 \text{ years} $$

Correct Option:

- Option:2, 3½ years

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