Percent growth is exponential: the SAT math trap

Short answer: "Percent each year" = multiply each year (exponential). "Same amount each year" = add (linear).

The trap, in one question

Tempting answer: 1,150  (+50 every year, linear)

Correct answer: About 1,158  (1,000(1.05)³ ≈ 1,157.6)

How to spot it in 3 seconds

"Percent each year" = multiply each year (exponential). "Same amount each year" = add (linear).

FAQ

What is the percent growth is exponential trap on the SAT?

Example: A town of 1,000 people grows by 5% each year. About how many people live there after 3 years? The tempting answer is 1,150 (+50 every year, linear); the correct answer is About 1,158 (1,000(1.05)3 ≈ 1,157.6).

How do you avoid the percent growth is exponential trap?

"Percent each year" = multiply each year (exponential). "Same amount each year" = add (linear).

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