Percentages
A percentage is a fraction expressed out of 100. "Per cent" literally means "per hundred".
Practice This ConceptUnderstanding Percentages
Percentages make fractions easier to understand by expressing everything out of 100. When you say "25%", you mean 25 out of 100, or 1/4. In EPSO, almost every answer is expressed as a percentage. The critical skill is converting between raw numbers and percentages quickly.
Formula
$percentage = \frac{part}{whole} \times 100$
Key Rules
- To convert a decimal to a percentage: multiply by 100 (0.15 → 15%)
- To convert a percentage to a decimal: divide by 100 (15% → 0.15)
- Percentage points ≠ percentage change (going from 10% to 15% is +5 percentage POINTS but +50% change)
- A percentage can be more than 100% (if the part is bigger than the reference)
Examples in Action
1
0.1001 × 100
=
10.01%
Converting GDP growth fraction to percentage
2
25% of 800
=
200
25/100 × 800 = 200
3
150 out of 200
=
75%
150/200 × 100 = 75%
Common Errors
- Forgetting to multiply by 100 (leaving answer as 0.15 instead of 15%)
- Confusing percentage points with percentage change
- Applying a percentage to the wrong base number
Pro Tip
When you see a decimal like 0.067, immediately think "move the decimal point 2 places right" → 6.7%.