At what rate per cent per annum will Rs. 630 produce an interest of Rs. 126 in 4 years ?

Answer

To find the rate of interest per annum that will produce an interest of Rs. 126 on a principal of Rs. 630 in 4 years, we can follow these steps:

### Step 1: Identify the given values
- Principal (P) = Rs. 630
- Simple Interest (SI) = Rs. 126
- Time (T) = 4 years

### Step 2: Use the formula for Simple Interest
The formula for Simple Interest is:
\[ SI = \frac{P \times R \times T}{100} \]
where:
- SI = Simple Interest
- P = Principal
- R = Rate of interest per annum
- T = Time in years

### Step 3: Substitute the known values into the formula
Substituting the values into the formula gives:
\[ 126 = \frac{630 \times R \times 4}{100} \]

### Step 4: Simplify the equation
To simplify, first multiply both sides by 100 to eliminate the fraction:
\[ 126 \times 100 = 630 \times R \times 4 \]
This simplifies to:
\[ 12600 = 2520R \]

### Step 5: Solve for R
Now, divide both sides by 2520 to isolate R:
\[ R = \frac{12600}{2520} \]
Calculating this gives:
\[ R = 5 \]

### Step 6: State the final answer
Thus, the rate of interest per annum is:
\[ R = 5\% \]

### Summary
The rate per cent per annum at which Rs. 630 will produce an interest of Rs. 126 in 4 years is **5%**.

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