Percentages are everywhere — discounts, tax rates, exam scores, interest rates, nutrition labels. Yet many people reach for their phone calculator every time they need one. Once you understand the three core percentage formulas, you can handle any percentage problem confidently.
Every percentage question falls into one of three types:
Type 1: Find the percentage of a number
Type 2: Find what percentage one number is of another
Type 3: Find the original number from a percentage
| Problem | Formula | Answer |
|---|---|---|
| What is 20% of 350? | (20÷100) × 350 | 70 |
| 45 is what % of 180? | (45÷180) × 100 | 25% |
| 60 is 30% of what? | 60 ÷ (30÷100) | 200 |
| Price after 15% discount on $80? | 80 − (15÷100 × 80) | $68 |
| % increase from 50 to 75? | ((75−50)÷50) × 100 | 50% |
If interest rates rise from 3% to 5%, that's an increase of 2 percentage points — but a 66.7% increase in the rate itself. These are different things and often confused in news reporting.
Subtract the old value from the new value, divide by the old value, then multiply by 100. Formula: ((New − Old) ÷ Old) × 100.
Multiply the number by (1 + percentage/100). Adding 20% to 150: 150 × 1.20 = 180.
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