Percentage Increase & Decrease Practice Problems & Step Solutions
Master calculating percentage change and applying growth/decay in real-world scenarios. Practice finding percent discounts, sales tax markup, and relative percentage difference.
🧠 Core Problem-Solving Strategies
⚡ The Decimal Multiplier Method
To increase by 20%, multiply by 1.20. To decrease by 15%, multiply by (1 − 0.15) = 0.85.
📊 Percentage Change Formula
% Change = ((New Value − Original Value) / Original Value) × 100%. Always divide by the ORIGINAL amount!
🖐️ 10% & 1% Mental Building Blocks
Find 10% by shifting decimal 1 place left. Double for 20%, halve for 5%.
❓ Frequently Asked Questions
Why must you divide by the original value when calculating percentage change?
Because percentage change measures growth or decay relative to where you started (the baseline).
What is the difference between percent increase and percent decrease?
Percent increase measures positive growth above original (e.g. +20%), while percent decrease measures negative reduction below original (e.g. −15%).
Continue Learning & Practicing
Reinforce your understanding with printable worksheets, step-by-step guides, calculators, and speed games: