Percentages without a calculator
Find 10%, 5%, 25%, and everything in between using a few easy pieces.
Start with what percent means
Percent means “out of 100”. So 20% is 20 out of every 100, or one fifth. To find 20% of 60, you can calculate 60 × 20 ÷ 100 = 12. That general rule always works, but there are often easier mental steps.
Find 10%, then build
Divide a number by 10 to find 10%. For 80, that is 8. Double it for 20%: 16. Halve it for 5%: 4. Add 10% and 5% for 15%: 12. This is especially handy when a number does not divide neatly by 100 in your head.
Use familiar fractions
50% is one half, 25% is one quarter, and 75% is three quarters. For 25% of 64, divide 64 by 4: 16. For 75% of 64, multiply that quarter by 3: 48. You can also subtract 25% from the whole: 64 − 16 = 48.
Keep the discount separate from the final price
A 20% discount on 70 is 14, because 10% is 7 and 20% is 14. The final price is 70 − 14 = 56. Answering “14” gives the size of the discount, not the amount left to pay. Read which quantity the question asks for.
Try it, then check
Find 5% of 120, 15% of 60, and 25% of 88. Answers: 6, 9, and 22. For the middle question, 10% is 6 and 5% is 3, so 15% is 9.
Take your time with a free set of percentages questions and worked answers.
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