15% off 20 is 17 — you save 3.
Worked out below step by step, with a table of related values and a live calculator so you can change the numbers.
Check it: 17 + 3 = 20, the original price.
sale price = value − (percent ÷ 100) × value
A discount is the percentage taken away, so the price you pay is the original value minus that amount.
A discount has two separate values: the amount removed and the final price. First calculate 15% of 20, which is 3. Then subtract that discount from the original 20.
The final amount is 17. Showing both figures prevents a common mistake: reporting the discount itself when the question asks for the price after the discount.
Instead of finding the discount and subtracting it, calculate the part that remains after the discount. A 15% discount leaves 85% of the original 20.
What is 15% off 40?
Find the discount: 15 ÷ 100 × 40 = 6. Subtract it from the original value: 40 − 6. You save 6 and pay 34. This uses the same method with different numbers, so it shows how the rule transfers instead of only repeating the original answer.
A 15% discount removes 3 from 20 and leaves 85% of the original amount. The retained-value multiplier is 0.85, which leads to the final value 17.
This method applies to sale prices, negotiated reductions, coupon discounts and budget savings. Keeping the discount amount and the final amount separate helps when checking receipts, comparing offers or explaining a price reduction.
Instead of finding the discount and subtracting it, calculate the part that remains after the discount. A 15% discount leaves 85% of the original 20. Remaining percentage = 100% − 15% = 85%. Convert 85% to 0.85. 20 × 0.85 = 17.
Reporting the discount amount as the final price instead of subtracting the discount from the original amount. After correcting that setup, verify the result independently: Check it: 17 + 3 = 20, the original price.
Yes. What is 15% off 40? Find the discount: 15 ÷ 100 × 40 = 6. Subtract it from the original value: 40 − 6. You save 6 and pay 34. This uses the same method with different numbers, so it shows how the rule transfers instead of only repeating the original answer. The live calculator above lets you replace both inputs and recalculate without changing the underlying method.
A 15% discount removes 3 from 20 and leaves 85% of the original amount. The retained-value multiplier is 0.85, which leads to the final value 17. Use that scale or ratio check together with the reverse calculation before reusing the result in another calculation.
| Discount | You pay |
|---|---|
| 1% off | 19.8 |
| 5% off | 19 |
| 10% off | 18 |
| 15% off | 17 |
| 20% off | 16 |
| 25% off | 15 |
| 30% off | 14 |
| 40% off | 12 |
| 50% off | 10 |
| 60% off | 8 |
| 75% off | 5 |
| 100% off | 0 |