A shop board says: "20% off, then an extra 10% off on that." Geeta says that makes 30% off in total

Why

Adding 20 and 10 to get 30 feels natural, and Geeta's right that two discounts should beat one. The hidden move is WHAT each percent is taken from. The 20% comes off the full price, but the 10% comes off the ALREADY-reduced price — a smaller amount — so it's worth less than a 10% off the original. Try ₹100: 20% off leaves ₹80; then 10% of ₹80 is ₹8, leaving ₹72. Total saved is ₹28, so it's 28% off, not 30. The shopkeeper smiles because '20+10' sounds bigger than what he actually gives. Test: percentages only add up when they're slices of the SAME whole; here the second slice is cut from a smaller cake. Geeta is not right — stacked discounts come to less than their sum, because each new percent works on a shrunk price.