Math
Treating Percent Increase and Decrease as Reversible
Students think a percent increase and the same percent decrease cancel each other out.
Quick check
Why students make it
The percent number looks the same in both steps, so it feels like adding and subtracting the same amount. The mistake is ignoring that the second percent is taken from a new base value.
The rule done right
A percent increase by multiplies by , and a percent decrease by multiplies by . These are not usually reversible because the bases are different.
Related resources
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Math, Percent Change Infographic -
Math, Percent Word Problems Infographic -
Math, Fraction-Decimal-Percent Conversions Infographic -
The Math of Tipping and Splitting the Bill Infographic - Fractions, Decimals & Percents Cheat Sheet
- Pre-Algebra Foundations Cheat Sheet
- Ratios, Rates & Proportions Cheat Sheet
- Percent Word Problems Reference Cheat Sheet
- How to set up a percent proportion Memory Aid Cheat Sheet
- Math, Percent Increase and Decrease Worksheet
- Math, Percent of a Number Worksheet
- Percent Discount and Tax Worksheet
- Math, How to Set Up a Percent Proportion Practice Worksheet
- Ratios & Proportions Worksheet
- Percent Calculator & Visualizer Tool
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- Ratio, Proportion & Percent Lab Lab
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