Why Stacked Discounts Do Not Simply Add
A second discount applies to the price remaining after the first discount. For example, 20% off followed by another 10% off reduces a $100 price to $72, which is a 28% combined discount rather than 30%.
The calculator limits each entered discount to the meaningful range from 0% to 100%, preventing negative prices caused by percentages above 100%.
Stacked discounts are a good example of why percentages should be applied to the correct base. If an item is reduced by 20% and then by another 10%, the second discount applies to the already reduced price, not to the original price. The final discount is therefore 28%, not 30%. The same logic works for any sequence of valid discounts and is useful when a promotion combines a sale price with a coupon or member discount.
Frequently Asked Questions
Is 20% off plus 10% off the same as 30% off?
No. The second 10% applies after the first discount. A $100 price becomes $80 and then $72, for a 28% effective combined discount.
Why can I not simply add two discount percentages together?
Because the second percentage is normally applied after the first reduction. It is calculated from a smaller price, so the combined effective discount is less than the arithmetic sum.
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