In a sale there is a 30 percent discount on the marked price of 2,500 rupees, but an item is actually sold for only 1,400 rupees. What additional discount percentage, beyond the 30 percent sale discount, did the customer effectively receive?

Introduction / Context:
This problem explores the idea of an extra discount applied after a sale discount. The marked price, sale discount, and final selling price are all given, and you must compute the additional discount percentage that explains the further reduction. This type of multi step discount calculation is common in real life promotions and exam questions.

Given Data / Assumptions:
- Marked price (MP) of the item = 2,500 rupees.
- Advertised sale discount = 30 percent on the marked price.
- Actual selling price (SP final) = 1,400 rupees.
- First, compute the sale price after the 30 percent discount.
- Then find what extra discount was given from that sale price down to 1,400 rupees, expressed as a percentage of the sale price.

Concept / Approach:
The solution consists of two phases: initial sale discount and additional discount. First calculate the price after the 30 percent sale, which is 70 percent of the marked price. Then treat the further reduction from that price to 1,400 rupees as a new discount and compute its percentage relative to the sale price. The base for the additional discount percent is the sale price, not the marked price.

Step-by-Step Solution:
Step 1: After a 30 percent discount on 2,500 rupees, the customer should pay 70 percent of the marked price.Step 2: 70 percent of 2,500 = 0.70 * 2,500 = 1,750 rupees.Step 3: However, the item is actually sold for 1,400 rupees.Step 4: Extra discount amount beyond the 30 percent sale = 1,750 - 1,400 = 350 rupees.Step 5: Additional discount percentage = (Extra discount / Sale price) * 100.Step 6: Substitute values: (350 / 1,750) * 100.Step 7: 350 / 1,750 = 1 / 5 = 0.20, so additional discount percentage = 0.20 * 100 = 20 percent.

Verification / Alternative check:
Check in one combined view. The marked price is 2,500. A 30 percent discount reduces it to 1,750. An additional 20 percent discount on 1,750 is 0.20 * 1,750 = 350, which brings the price down to 1,750 - 350 = 1,400 rupees. This matches the given final selling price, confirming that the extra discount is indeed 20 percent.

Why Other Options Are Wrong:
- 10 percent or 15 percent additional discount would not reduce 1,750 down to 1,400; they would leave a higher final selling price.
- 25 percent extra discount would reduce 1,750 by 437.5 rupees, giving a selling price of 1,312.5 rupees, which is too low compared to the given 1,400 rupees.

Common Pitfalls:
One common mistake is to compute the additional discount percentage using the marked price as the base instead of the already reduced sale price. Another is to directly compare 2,500 and 1,400 and say the total discount is 44 percent and then try to subtract 30 percent to claim 14 percent extra. Successive discounts are multiplicative, so the extra discount must be computed on the already discounted value, not on the original marked price.

Final Answer:
The customer effectively received an additional 20 percent discount beyond the 30 percent sale discount.