How to find the price before tax: reverse percentages.
How to work back to a price before tax was added or a discount taken off, and why taking the percentage off again gives the wrong answer.
By Suraj Kumar3 min read
A receipt says 118 with 18% tax included. What was the price before the tax? The answer is not 118 minus 18%.
Divide, do not subtract.
Adding 18% multiplied the price by 1.18. To undo it, divide by 1.18: 118 ÷ 1.18 = 100. The Reverse percentage calculator shows this step and checks it by adding the 18% back on.
Why taking it off again is wrong.
18% of 118 is 21.24, and 118 − 21.24 is 96.76, not 100. The tax was 18% of the price before, which was smaller, so taking 18% of the price after takes off too much. The page shows both so the difference is plain.
Undoing a discount.
After 20% off, a price is 80% of what it was, so divide by 0.8: 80 was 100 before the discount. Choose Taken off on the page.
Further reading
Topics: reverse percentage · price before tax · original price · remove vat · remove gst · reverse percentage calculator
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