A discount multiplies the price by what is left: 25% off means paying 75%, so 80 × 0.75 = 60.
Stacked discounts are applied one after another, not added together. 25% off and then an extra 10% off is 0.75 × 0.90 = 0.675 of the price, a total of 32.5% off — not 35%.
Final = Price × (1 − d₁) × (1 − d₂)
d₁, d₂ — discounts as decimals
Common questions
How do I work out the original price from a sale price?
Divide by what is left after the discount: a sale price of 60 after 25% off is 60 ÷ 0.75 = 80.
Is 50% off plus 20% off the same as 70% off?
No. It is 0.5 × 0.8 = 0.4 of the price, which is 60% off.