1. What the question asks We need the final price of a 2500 rupee shirt after a 20% discount is taken off, and then 10% sales tax is added to the discounted price. 2. The key idea A percentage is a part out of 100. A discount makes the price smaller, so we keep 80% of the price (100% - 20%). Tax makes the price bigger, so we pay 110% of the new price (100% + 10%). The tax is worked out on the discounted price, not on the original 2500. That is why we do the two changes one after the other. 3. Step-by-step solution Step 1: Find the discount amount. 20% of 2500 = 20/100 x 2500 = 500. We do this to know how much the shop takes off. Step 2: Subtract the discount. 2500 - 500 = 2000. This is the discounted price, and it is the base for the tax. Step 3: Find the tax amount. 10% of 2000 = 10/100 x 2000 = 200. We use 2000 (not 2500) because the question says tax is added on the discounted price. Step 4: Add the tax. 2000 + 200 = 2200. This is the final price. Final price = 2200 rupees. 4. Check (a different method) Use multipliers instead of finding the amounts separately. Keeping 80% means multiplying by 0.80. Adding 10% means multiplying by 1.10. 2500 x 0.80 = 2000 2000 x 1.10 = 2200 Both methods give 2200 rupees, so the answer is correct. 5. Common mistake to avoid Many students add the percentages and think "-20% + 10% = -10%", so they take 10% off 2500 and get 2250. This is wrong because the 10% tax is worked out on 2000, a smaller number, not on 2500. Percentages applied one after another cannot simply be added or subtracted. 6. Try it yourself A bag costs 4000 rupees. The shop gives a 25% discount, then adds 5% sales tax on the discounted price. What is the final price? Answer: 3150 rupees