SAT Math: Apply successive (stacked) percent changes
21+ practice questions in Praczo
The concept, explained
- 1
Successive percent changes do NOT add. A 20% increase followed by a 20% decrease does not cancel — you end up below the original.
- 2
Instead, multiply the change factors. A 20% increase = multiply by 1.20; then a 20% decrease = multiply by 0.80. Net factor = 1.20 · 0.80 = 0.96, a 4% decrease overall.
- 3
For a sequence of changes: multiply all factors together, then subtract 1 to find the net percent change.
- 4
Order does not matter for multiplication, but be careful which base each percent is applied to.
- ✗ Adding percent changes instead of multiplying the factors.
- ✗ Forgetting that the second percent is applied to the new value, not the original.
SAT-style practice
A stock price increased by 30% in January and then decreased by 10% in February. What was the overall percent change?
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