Discount stack calculator
Stacked discounts multiply. Thirty per cent off then twenty per cent off leaves 56% of the original price: an effective 44% discount, not 50%. The shortfall grows as the individual percentages grow.
How to combine discounts
The order does not matter; 30% then 20% gives the same answer as 20% then 30%, but the intuition that they add certainly does. The mathematical reason is that the second discount applies to the already-reduced price, so it takes a percentage of a smaller number. Two 50% discounts leave a quarter of the price, not nothing. This matters most on the retailer side, where a stack of promotions each individually approved can quietly take a product below cost.
Questions
No. Applied in sequence they give 44% off, because the second applies to the already-reduced price.
No. Multiplication is commutative, so the final price is the same either way.
Seventy-five per cent off, leaving a quarter of the price. Never free.
Multiply the remaining fractions and subtract from one: 0.7 × 0.8 = 0.56, so 44% off.
Only if the terms allow it. Many are explicitly not combinable, and some apply before rather than after a sale price.