Percent Increase & Decrease

Practise increasing and decreasing a number by a percentage — the math behind discounts, tips and price rises.

Grades 6–7 · 7.RP⚡ Real-world math
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How to increase or decrease by a percent

This is the everyday percentage skill — sale discounts, tips, tax, price rises. The reliable method is to find the percentage amount first, then add it on or take it off.

  1. Find that percent of the number (percent × number).
  2. For an increase, add it to the original; for a decrease, subtract it.
  3. Shortcut: a 25% increase is the same as multiplying by 1.25; a 25% decrease, by 0.75.

Worked examples

IncreaseIncrease 40 by 25% — 25% of 40 is 10, so 40 + 10 = 50.
DecreaseDecrease 80 by 10% — 10% of 80 is 8, so 80 − 8 = 72.
AD AREA (parent reading zone only — never shown during practice)

Tips & common mistakes

The most common real-world version is a sale price: “30% off” means find 30% and subtract. Once kids are comfortable, the one-step multiplier (×1.30 to add 30%, ×0.70 to take it off) is faster. Type your answer with the decimal-point key if needed.

  • Finding the percentage but forgetting to add or subtract it from the original.
  • Subtracting for an increase or adding for a decrease — read the question.
  • Using the multiplier the wrong way (×0.30 instead of ×1.30 for a 30% increase).

Frequently asked questions

How do you increase a number by a percent?

Find that percent of the number, then add it on. Increasing 40 by 25%: 25% of 40 is 10, so the answer is 50.

How do you decrease a number by a percent?

Find the percent of the number and subtract it. Decreasing 80 by 10%: 10% of 80 is 8, so the answer is 72.

What’s the one-step multiplier method?

For a 25% increase, multiply by 1.25; for a 25% decrease, multiply by 0.75. It combines both steps into one.

How is this used in real life?

Sale discounts, tips, sales tax and price changes are all percent increase or decrease.

What grade is this?

Percent increase and decrease is a grade 6–7 skill, central to proportional reasoning.

Keep practising

← All percentagesPercent of a numberFinding the percent7th grade math

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