During a sale, a shop announces a 40% discount on the marked price of Rs 1000 for a product, but a customer finally buys it for Rs 510. What additional discount percentage (over and above the announced 40% on the marked price) did the customer effectively receive?

Introduction / Context:

This question involves interpreting discounts in two stages. First, there is an announced discount on the marked price, and then there is an additional price reduction leading to an even lower selling price. You are asked to compute how much extra discount, as a percentage of the already reduced sale price, the customer obtained beyond the advertised discount.

Given Data / Assumptions:

• Marked price of the product = Rs 1000.
• Announced discount = 40% on the marked price.
• Expected sale price after 40% discount = 60% of 1000.
• Actual selling price to the customer = Rs 510.
• We must find the additional discount percentage on the price after the 40% discount.

Concept / Approach:

The first step is to compute the normal discounted price with a 40% reduction. Then, compare this intended sale price with the actual price paid. The difference between these two amounts is the extra discount. Since the question asks for additional discount, we interpret it as a percentage of the price after the 40% discount, not again on the original marked price.

Step-by-Step Solution:

Verification / Alternative check:

We can also calculate the total discount directly from the marked price. Total discount = 1000 − 510 = Rs 490. Total discount percentage on marked price = 490 / 1000 * 100 = 49%. The announced discount was 40%. The difference between total discount (49%) and announced discount (40%) is 9%. However, this 9% is relative to the marked price, not the extra discount relative to the reduced sale price. The question explicitly talks about additional discount after the 40% reduction, which we correctly computed as 15% based on the Rs 600 price.

Why Other Options Are Wrong:

• 10%: If the extra discount were 10% of Rs 600, the reduction would be Rs 60, leading to a price of Rs 540, not Rs 510.
• 25% and 30%: These would imply much larger reductions from Rs 600, giving prices lower than Rs 510.
• 20%: An extra 20% on Rs 600 would be Rs 120, so the price would drop to Rs 480, which is not the actual selling price.

Common Pitfalls:

Many students mistakenly compute the difference between 49% and 40% as 9% and treat that as the answer. This ignores that the extra discount is usually interpreted as a percentage of the price after the first discount, not of the original price. Always clarify which base you are using for the percentage, especially when phrases like additional discount or extra discount are used.

Final Answer:

The additional discount over the already reduced sale price is 15%.