The cost of 7 pens is Rs42, then the cost of 4 pens is ?

Answer

To find the cost of 4 pens when the cost of 7 pens is Rs 42, we can use the unitary method. Here’s a step-by-step solution:

### Step 1: Find the cost of 1 pen
Given that the cost of 7 pens is Rs 42, we can find the cost of 1 pen by dividing the total cost by the number of pens.

\[ \text{Cost of 1 pen} = \frac{\text{Total cost of 7 pens}}{\text{Number of pens}} = \frac{42}{7} = 6 \]

### Step 2: Calculate the cost of 4 pens
Now that we know the cost of 1 pen is Rs 6, we can find the cost of 4 pens by multiplying the cost of 1 pen by 4.

\[ \text{Cost of 4 pens} = \text{Cost of 1 pen} \times 4 = 6 \times 4 = 24 \]

### Final Answer
Thus, the cost of 4 pens is Rs 24.

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