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Final price from two successive discounts
Convert each rate to the share it leaves behind, then multiply. For 200, 0.20 and 0.10 the result is 200 x 0.80 x 0.90 = 144.0.
The Formula
Final = Price x (1 - a) x (1 - b)
Convert each rate to the share it leaves behind, then multiply. For 200, 0.20 and 0.10 the result is 200 x 0.80 x 0.90 = 144.0.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| P | Original price | currency | The figure both discounts act on, indirectly. 200 in the standard case. |
| a | First discount as a decimal | decimal | 20% enters as 0.20, leaving the survival factor 0.80. |
| b | Second discount as a decimal | decimal | 10% enters as 0.10, leaving the survival factor 0.90, and it acts on the reduced price. |
What Each Symbol Means
Pcurrency
Original price
The figure both discounts act on, indirectly. 200 in the standard case.
adecimal
First discount as a decimal
20% enters as 0.20, leaving the survival factor 0.80.
bdecimal
Second discount as a decimal
10% enters as 0.10, leaving the survival factor 0.90, and it acts on the reduced price.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate stacked discounts page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Stacked Discounts, filed under Everyday Life. Every number the guide produces comes from substituting into this one line.