The Discount Formula
Sale Price = Original Price × (1 − Discount %)
Stacking Two Discounts
When two discounts apply (like "25% off, plus an extra 10% off"), they are applied sequentially, not added together. A 25% discount followed by an additional 10% discount is not the same as a single 35% discount — it works out to a smaller total discount, since the second discount applies to the already-reduced price.
Final Price = Original Price × (1 − Discount 1) × (1 − Discount 2)
Why This Matters When Shopping
Retailers sometimes advertise stacked discounts in a way that can make the total savings seem larger than it actually is. Understanding that discounts compound multiplicatively (not additively) helps you accurately judge whether a "25% + 10% off" deal is actually better than a straightforward "35% off" deal (it's not — the stacked version saves less).