The cost of 4 Books and 7 Registers is Rs. 1250. What is the cost of 12 books and 21 Registers?

Options

A. Rs. 3250
B. Rs 3750
C. Rs. 3700
D. Can't be determined

Answer

To find the cost of 12 books and 21 registers based on the information given, we can use a proportionality approach.

### Step-by-Step Solution:

1. **Understand the given information**:
We know that the cost of 4 books and 7 registers is Rs. 1250.

2. **Set up the ratio**:
The ratio of books to registers in the first scenario is 4 books to 7 registers.

3. **Find the cost of 1 book and 1 register**:
Let's denote the cost of one book as \( B \) and the cost of one register as \( R \). From the equation:
\[ 4B + 7R = 1250 \]

4. **Scale the quantities**:
We need to find the cost of 12 books and 21 registers. Notice that 12 books and 21 registers are 3 times the quantities of 4 books and 7 registers:
\[ 12 = 3 \times 4 \quad \text{and} \quad 21 = 3 \times 7 \]

5. **Calculate the total cost**:
Since the cost is proportional to the quantities, we can multiply the total cost of 4 books and 7 registers by 3:
\[ \text{Cost of 12 books and 21 registers} = 3 \times 1250 = 3750 \]

6. **Final answer**:
Therefore, the cost of 12 books and 21 registers is Rs. 3750.