Percent problems

Learning goals

• Translate a percent change into a multiplier.
• Recover the original amount after an increase or decrease.

Explanation

A percent increase can be represented by new value = original value × (1 + rate). A 20% increase means multiplying by 1.20. A 20% decrease means multiplying by 0.80.

Common mistakes

• Using the new value as the base when the problem asks for percent of the original.
• Adding 20% twice and thinking that matches a 40% increase from the start.

Quick review

1. 01Write the multiplier before you compute.
2. 02Name the base of the percent in words.
3. 03Estimate so a 30% change cannot become a 3% answer unnoticed.

Related resources

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  Official SAT practice hub

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  Bluebook full-length practice

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  Student Question Bank

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  Official SAT Prep on Khan Academy

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  OpenStax College Algebra 2e

  Algebra reference; current terms include noncommercial and AI-ingestion limits.

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