How this number is made
Two discounts in a row are not the sum of the percents. Twenty percent off and then ten percent off leaves 72% of the price, not 70%. Stores stack them because the second percent applies to a smaller number.
- The order does not change the final price. It changes the intermediate tag.
- A third discount is another multiplication. This page stops at two.
Formula
Final = price × (1 − first) × (1 − second).
Worked example
With the figures already in the form, price after both discounts is $144.00.
Questions
Why isn’t it 30% off?
Because the second discount is 10% of what is left, not 10% of the original. The combined discount here is 28%, not 30%.
What about a coupon after a sale?
That is this page. Type the sale as the first discount and the coupon as the second.