A stationer buys pens at 5 for Rs 28 and sells them at a profit of 25%. How much should a customer pay, if he buys
only one pen?

Answer

To solve the problem step by step, we will follow these calculations:

### Step 1: Calculate the Cost Price (CP) of One Pen
The cost price of 5 pens is given as Rs 28.

To find the cost price of one pen, we divide the total cost by the number of pens:
\[ \text{CP of 1 pen} = \frac{28}{5} = 5.6 \text{ Rs} \]

### Step 2: Calculate the Profit
The profit percentage is given as 25%. To find the profit in terms of the cost price, we can use the formula:
\[ \text{Profit} = \text{Profit Percentage} \times \text{CP} \]
Substituting the values:
\[ \text{Profit} = 0.25 \times 5.6 = 1.4 \text{ Rs} \]

### Step 3: Calculate the Selling Price (SP) of One Pen
The selling price can be calculated using the formula:
\[ \text{SP} = \text{CP} + \text{Profit} \]
Substituting the values we found:
\[ \text{SP} = 5.6 + 1.4 = 7 \text{ Rs} \]

### Conclusion
Thus, if a customer buys only one pen, he should pay Rs 7.

---