Concept 1 · free preview
Meaning of percent and fraction values
Understand
Percent means ‘per hundred’. x% = x/100. So x% of N = N × x/100 — a percentage is just a fraction.
| Fraction | Percentage | Fraction | Percentage |
|---|---|---|---|
| 1/2 | 50% | 1/7 | 14 2/7 % |
| 1/3 | 33⅓% | 1/8 | 12.5% |
| 1/4 | 25% | 1/9 | 11 1/9 % |
| 1/5 | 20% | 1/10 | 10% |
| 1/6 | 16⅔% | 1/11 | 9 1/11 % |
| 3/8 | 37.5% | 1/12 | 8⅓% |
Example
45% of 360 = 360 × 45/100 = 162 12.5% of 640 = 640 × 1/8 = 80
Rule
x% of y = y% of x — pick the easier one: 16% of 25 = 25% of 16 = 4
Fraction → %: multiply by 100 (3/8 × 100 = 37.5%)
% of % of: multiply them all — 10% of 20% of 5000 = 5000 × 0.1 × 0.2 = 100
Common mistake
Do not read 0.5% as 50% or 5%. 0.5% of 1800 = 1800 × 0.5/100 = 9.
Check yourself
12.5% of 640 = ?
Answer: 80. (1/8 of 640)