The simple interest on ₹ 10 for 4 months at the rate of 3 paise per rupee per month is

### Concept & Formula When the rate of interest is given per month and the time is given in months, you do not need to convert time into years. You can use the standard simple interest logic directly. $$SI = Principal \times Rate_{monthly} \times Time_{months}$$ ### Step-by-Step Solution 1. **Given:** Principal = ₹ 10, Time = 4 months. 2. **Rate Analysis:** The rate is given as "3 paise per rupee per month". 3 paise = ₹ 0.03. This means the interest generated on ₹ 1 in 1 month is ₹ 0.03. 3. Calculate the interest on ₹ 10 for 1 month: Interest for 1 month = $10 \times 0.03 = 0.30$ 4. Calculate the interest for the full time period (4 months): Total Simple Interest = $0.30 \times 4 = 1.20$ ### Exam Strategy & Shortcut The rate "3 paise per rupee" translates exactly to 3% (since 3 paise is 3/100 of a rupee). Therefore, the rate is simply 3% per month. $SI = \frac{10 \times 3 \times 4}{100} = \frac{120}{100} = 1.20$. ### Common Pitfall A frequent error is automatically dividing the time by 12 to convert months to years without noticing that the interest rate provided is already on a *per month* basis. Doing so would incorrectly yield ₹ 0.10 as the answer. ### Final Answer Therefore, the correct answer is **₹ 1.20**.