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To find the discount percentage: subtract the sale price from the original price, divide by the original price, multiply by 100. Formula: ((Original - Sale) / Original) x 100. An item marked down from $120 to $84 is 30% off.
| Goal | Formula | Example |
|---|---|---|
| Find discount % | ((Original - Sale) / Original) x 100 | ($120 - $84) / $120 x 100 = 30% |
| Find sale price | Original x (1 - Discount%/100) | $120 x 0.70 = $84 (30% off) |
| Find original price | Sale / (1 - Discount%/100) | $84 / 0.70 = $120 |
You do not need a calculator for most discounts. These shortcuts let you calculate in your head while shopping:
| Discount | Mental Shortcut | Example ($80 item) |
|---|---|---|
| 10% off | Move decimal one left | $80 → $8 off → pay $72 |
| 15% off | 10% + half of 10% | $8 + $4 = $12 off → pay $68 |
| 20% off | 10% x 2, or divide by 5 | $8 x 2 = $16 off → pay $64 |
| 25% off | Divide by 4 | $80 / 4 = $20 off → pay $60 |
| 30% off | 10% x 3 | $8 x 3 = $24 off → pay $56 |
| 33% off | Divide by 3 | $80 / 3 \u2248 $27 off → pay \u2248$53 |
| 40% off | Half - 10% | $40 - $8 = $32 off → pay $48 |
| 50% off | Divide by 2 | $80 / 2 = $40 off → pay $40 |
| 75% off | Quarter of original | $80 / 4 = $20 → pay $20 |
These formulas calculate pre-tax discounts. The actual checkout price will include sales tax (applied after discounts in most US states). The formulas also do not account for tiered pricing, loyalty discounts, cashback, or coupon stacking rules — which vary by retailer.
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