SAT and ACT math terms · SAT Math, ACT Math
Percent change
Percent change: The change in a quantity expressed as a percentage of the original value: (new − original) / original × 100.
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What it means
Percent increase and decrease are always calculated relative to the starting value. A shortcut is to use multipliers: a 20% increase multiplies by 1.20, and a 20% decrease multiplies by 0.80.
Successive percent changes multiply: a 20% increase followed by a 20% decrease gives 1.20 × 0.80 = 0.96, a 4% overall decrease.
Example
A price rises from $50 to $65. Percent change = (65 − 50) / 50 = 0.30, a 30% increase.
On the exam
Percentages appear in SAT Problem-Solving and Data Analysis and in ACT ratios, rates and percents questions.