Question
A shirt has a marked price of ₹800. The shopkeeper offers a 15% discount. Find the sale price.
Solution — Step by Step
Discount is always calculated on the marked price (also called MRP), not on any other value. Here, 15% of ₹800 gives us the rupee discount.
The sale price is what the customer actually pays — marked price minus the discount the shopkeeper gives away.
The shirt is sold for ₹680.
Why This Works
Percentage means “per hundred.” When we say 15% discount, we mean for every ₹100 of marked price, the shopkeeper cuts ₹15. So for ₹800, we scale that up: 15 × 8 = 120.
The sale price formula captures this directly: Sale Price = Marked Price − Discount. We’re not guessing — we’re finding the exact rupee value of the reduction first, then subtracting.
This two-step method (find discount amount → subtract) is the safest approach in board exams because each step is checkable. Never skip directly to the answer in one mental step during an exam.
Alternative Method
Instead of finding the discount separately, we can use the idea that if 15% is gone, then 85% remains.
The “remaining percentage” trick is faster once you’re comfortable. If discount = 15%, sale price = (100 − 15)% of MRP = 85% of MRP. This saves one step and is useful when exam questions ask for sale price directly without asking for discount amount separately.
This method appears frequently in Class 7 and 8 CBSE worksheets because it tests whether students understand that discount and sale price together make 100% of the marked price.
Common Mistake
Calculating 15% of the sale price instead of the marked price.
Students sometimes write: “Sale price = ₹800, discount = 15% of 800… then subtract again.” That’s circular and wrong. The discount is always on the marked price (MRP), which is ₹800 here. The sale price is the result, never the base for discount calculation — unless the question explicitly says otherwise (like “successive discounts,” which is a different topic).
A second trap: computing 800 − 15 = 785 and writing ₹785. This happens when students subtract the percentage number directly instead of the rupee value. Always convert percent to rupees first, then subtract.