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Percent Change Hacks

Don't get trapped by multi-step changes. Master the multiplier method.

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Heart of Algebra

Net Percent Change

\[ (1 \pm r_1)(1 \pm r_2) - 1 \]

Calculate the single percentage change for multi-step increases/decreases.

📝 Example: Multi-Step Change

"A price increases by 20%, then decreases by 10%."

🚫 School Way (45s)

Pick 100 → 120 → 108. Change is 8%.

✅ Practix Way (2s)

(1.20)(0.90) = 1.08. Answer = 8% Increase.

Heart of Algebra

Standard Percent Change

\[ \frac{\text{New} - \text{Old}}{\text{Old}} \times 100 \]

The universal formula for calculating percentage increase or decrease without confusion.

📝 Example: Basic Change

Price goes from $80 to $100. % Change?

\(\frac{100 - 80}{80} = \frac{20}{80} = 0.25 \rightarrow 25\%\)

Result: 25% Increase.