If the interest on money be 1 paisa per rupee per month, what is the rate per cent per annum?

Options

A. 12
B. 15
C. 11
D. `10 (1)/(2) `

Answer

To solve the problem of finding the rate of interest per annum when the interest is 1 paisa per rupee per month, we can follow these steps:

### Step 1: Understand the monthly interest
The problem states that the interest is 1 paisa per rupee per month. Since 1 rupee is equivalent to 100 paisa, we can express this as:
- Monthly interest = 1 paisa

### Step 2: Calculate the annual interest
To find the annual interest, we need to multiply the monthly interest by the number of months in a year:
- Annual interest = Monthly interest × 12 months
- Annual interest = 1 paisa × 12 = 12 paisa

### Step 3: Convert annual interest to rupees
Since we need to express the interest in terms of rupees, we convert 12 paisa to rupees:
- 12 paisa = 12/100 rupees = 0.12 rupees

### Step 4: Calculate the rate of interest per annum
The formula for calculating the rate of interest is:
\[ \text{Rate of Interest} = \left( \frac{\text{Annual Interest}}{\text{Principal}} \right) \times 100 \]
Here, the principal is 1 rupee. Thus, we can substitute the values:
- Rate of Interest = \(\left( \frac{0.12}{1} \right) \times 100\)

### Step 5: Simplify the calculation
Now, we can simplify the calculation:
- Rate of Interest = 0.12 × 100 = 12%

### Final Answer
The rate of interest per annum is **12%**.

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