A shop offers a deal: buy 4 dupattas at Rs. 1300 each and get 1 dupatta free.\nWhat is the effective discount percentage on each dupatta compared to the marked price?

Introduction / Context:
This problem deals with effective discount in a promotional offer of the type “buy some items and get one free.” Although no percentage is directly mentioned, such offers can be converted into equivalent percentage discounts by comparing the total amount paid with the total number of items received. This is a common scenario in retail marketing and exam questions.

Given Data / Assumptions:

• Marked price of one dupatta = Rs. 1300.
• Customer buys 4 dupattas and gets 1 dupatta free.
• Customer pays only for 4 dupattas but receives 5 dupattas in total.
• We need the effective discount percentage on each dupatta relative to its marked price.

Concept / Approach:
The total marked price of 5 dupattas would be 5 times the marked price, but the customer pays only for 4. So, the customer effectively pays a lower average price per dupatta than the marked price. To find the effective discount percent, compute the average price per dupatta that the customer pays, compare it to the marked price, and convert the difference into a percentage of the marked price.

Step-by-Step Solution:
Step 1: Marked price per dupatta = Rs. 1300. Step 2: For 5 dupattas at marked price, total would be 5 * 1300 = Rs. 6500. Step 3: Under the offer, the customer pays only for 4 dupattas: 4 * 1300 = Rs. 5200. Step 4: Effective price per dupatta = total paid / total dupattas received = 5200 / 5 = Rs. 1040. Step 5: Discount per dupatta = marked price - effective price = 1300 - 1040 = Rs. 260. Step 6: Effective discount percentage = (260 / 1300) * 100 = 20%.

Verification / Alternative check:
We can also compare the ratio of effective price to marked price: 1040 / 1300 = 0.8. This means the customer is paying 80% of the marked price per dupatta. Hence the discount is 100% - 80% = 20%. This matches the earlier calculation, confirming that the effective discount per dupatta is 20%.

Why Other Options Are Wrong:
12.5%: Would correspond to paying 87.5% of the marked price; the offer here is more generous than that.
25% and 33.33%: These are larger discounts than actually provided by the buy 4 get 1 free arrangement at this price point.
50%: This would mean paying only half the marked price per dupatta, which is clearly not the case here.

Common Pitfalls:
A frequent mistake is to assume the discount is 1 item out of 5, that is 20%, without checking if the prices are equal or more complex. In this question the prices are equal, so that logic works, but one must still demonstrate it through calculations. Another error is to calculate discount based on total marked price of 4 items instead of 5 items received, which leads to confusion.

Final Answer:
The effective discount on each dupatta is 20% of the marked price.