By selling a wristwatch for ₹3,960, a shopkeeper loses 10%. What was the cost price?

💡 Solution & Explanation

A 10% loss means the selling price is 90% of the cost price. So cost price = ₹3,960 × 100 ÷ 90 = ₹4,400. Check: 10% of ₹4,400 is ₹440, and ₹4,400 − ₹440 = ₹3,960. Adding 10% to ₹3,960 gives ₹4,356, which is wrong because the loss is a percentage of the cost, not of the selling price.