A salesman offers a discount scheme of 'Buy 25 and get 5 free' on the purchase of notebooks in his shop. He professes that a notebook costs him Rs. 10, but in reality, it costs him Rs. 5. Find the difference between his profit percentage and scheme discount.

Correct option is C

Given:
Scheme: Buy 25 and get 5 free → Total notebooks given = 30
Selling Price per notebook (professed) = Rs. 10
Cost Price per notebook (actual) = Rs. 5
Concept Used:
​$$\text{Profit \%} = \left( \frac{\text{Profit}}{\text{Cost Price}} \right) \times 100$$ 
​$$\text{Scheme Discount \%} = \left( \frac{\text{Free Items}}{\text{Total Items Received}} \right) \times 100$$​​
Solution:
Customer gets 5 notebooks free out of 30, so:
Scheme Discount % = $$\left( \frac{5}{30} \right) \times 100 = 16.67\%$$​​
Selling Price for 25 notebooks = 25 × 10 = Rs. 250
Cost Price for 30 notebooks = 30 × 5 = Rs. 150
Profit = 250 – 150 = Rs. 100
Profit % =$$\left( \frac{100}{150} \right) \times 100 = 66.67\%$$​​
Difference between Scheme Discount and Profit Percentage = 66.67% - 16.67% = 50%