A book has a marked price of Rs. 2150 and is sold for Rs. 1892. What is the discount percentage offered on the marked price?

Introduction / Context:
This question is a straightforward percentage discount problem. The marked price of a product is given, along with the selling price after discount. The task is to find what percentage discount the buyer received. Such problems are very common in commerce, shopping, and aptitude tests, and they reinforce the basic idea of percentage decrease from an original reference value.

Given Data / Assumptions:
Marked price (MP) of the book = Rs. 2150.
Selling price (SP) after discount = Rs. 1892.
Discount is calculated as the difference between MP and SP.
We need to find the discount percentage with respect to the marked price.

Concept / Approach:
The discount amount is MP minus SP. Once we know the discount amount, the discount percentage is given by (discount amount / marked price) * 100. Here, this translates to ((2150 - 1892) / 2150) * 100. It is important to remember that this percentage is always calculated on the marked price, since that is the reference value before any deduction. This simple formula provides the required percentage reduction.

Step-by-Step Solution:
Marked price MP = Rs. 2150. Selling price SP = Rs. 1892. Discount amount = MP - SP = 2150 - 1892. Compute 2150 - 1892 = 258. Discount percentage = (discount amount / MP) * 100. So, discount percentage = (258 / 2150) * 100. Compute 258 / 2150 = 0.12. Therefore discount percentage = 0.12 * 100 = 12 percent.

Verification / Alternative check:
We can verify by checking what 12 percent of 2150 is. Calculate 12 percent of 2150: (12 / 100) * 2150 = 0.12 * 2150 = 258. Subtract this discount from the marked price: 2150 - 258 = 1892, which matches the given selling price. This confirms that the discount percentage is indeed 12 percent and that there are no arithmetic errors in our calculation.

Why Other Options Are Wrong:
If the discount were 13 percent, then discount amount would be 13 percent of 2150 = 279.5, leading to a selling price of 1870.5, not 1892. For a 14 percent discount, the discount amount would be 301, and the selling price would become 1849, again incorrect. For a 15 percent discount, the selling price would reduce even further to 1827.5. None of these match the given selling price, so only 12 percent is consistent with the data.

Common Pitfalls:
Some candidates mistakenly use the selling price as the base and compute discount percentage relative to SP, which is not standard in discount problems. Others confuse the concept of profit and discount and try to relate the values to cost price instead of marked price. A few may also commit arithmetic errors by mixing up subtraction or by misplacing decimal points. To avoid such mistakes, always clearly identify the base (here, marked price), compute the difference, and then apply the formula percentage = (difference / base) * 100.

Final Answer:
The discount percentage offered on the book is 12 percent.