Percentages
5 minQuiz at the end
What is a Percentage?
A percentage (%) means per hundred β it's a way of expressing a number as a fraction of 100.
50% = 50 out of 100 = 1/2 = 0.5
Converting Between Formats
| Fraction | Decimal | Percentage |
|---|---|---|
| 1/2 | 0.5 | 50% |
| 1/4 | 0.25 | 25% |
| 3/4 | 0.75 | 75% |
| 1/5 | 0.2 | 20% |
| 1/10 | 0.1 | 10% |
Fraction β Percentage: divide numerator by denominator, Γ 100
- 3/4 = 0.75 Γ 100 = 75%
Percentage β Decimal: divide by 100
- 30% = 30 Γ· 100 = 0.30
Finding a Percentage of a Quantity
What is 30% of 200? β 0.30 Γ 200 = 60
Or: 10% of 200 = 20, so 30% = 3 Γ 20 = 60
Percentage Increase and Decrease
Increase: Multiply by (1 + percentage/100)
- Increase Β£80 by 20%: 80 Γ 1.20 = Β£96
Decrease: Multiply by (1 - percentage/100)
- Decrease Β£80 by 15%: 80 Γ 0.85 = Β£68
Finding the Original Value
If a price after 20% increase is Β£96:
- Original = 96 Γ· 1.20 = Β£80