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Percentage Calculator Guide
Master percentage calculations for shopping discounts, restaurant tips, grade calculations, and business metrics.
Common Percentage Calculations
What is X% of Y?
Example: What is 15% of 80?
80 × 0.15 = 12X is what % of Y?
Example: 20 is what % of 80?
(20 ÷ 80) × 100 = 25%% Increase/Decrease
From 50 to 75:
((75-50) ÷ 50) × 100 = 50%Discount Price
$100 with 30% off:
100 - (100 × 0.30) = $70Real-World Applications
| Scenario | Common % | Example |
|---|---|---|
| Restaurant Tips | 15-20% | $50 bill → $7.50-$10 tip |
| Sales Tax | 5-10% | $100 item → $105-$110 total |
| Store Discounts | 10-50% | $80 with 25% off → $60 |
| Interest Rates | 2-7% | $1000 at 5% → $50/year |
| Grade Weights | 10-40% | Final exam worth 30% |
Mental Math Tricks
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10%: Move decimal one place left (50 → 5)
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5%: Half of 10% (10% of 80 = 8, so 5% = 4)
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15%: Add 10% + 5% together
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20%: Double 10% or divide by 5
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