What you need to know
A fraction describes part of a whole. The bottom number, the denominator, tells you how many equal parts the whole has been cut into. The top number, the numerator, tells you how many of those parts you are talking about. In 34, the whole is cut into 4 equal parts and we have 3 of them.
Reading a fraction
- A pizza is cut into 8 equal slices and 5 slices have been eaten.
- The denominator is 8 (8 equal parts).
- The numerator is 5 (5 of those parts).
- The fraction eaten is 58. The fraction left is 38, because 5 + 3 = 8.
Fractions on a number line. Fractions are numbers, so they sit on a number line between 0 and 1. If you split the space from 0 to 1 into 4 equal jumps, the marks are 14, 24, 34 and then 44, which is the same as 1. Counting in quarters sounds like: one quarter, two quarters, three quarters, one whole.
Equivalent fractions
Equivalent fractions are different names for the same amount. Half a sandwich is the same as two quarters of the sandwich: 12 = 24 = 48. You make an equivalent fraction by multiplying the numerator and the denominator by the same number. Multiplying both by 2 cuts every piece in half, so you have twice as many pieces that are each half the size — the amount does not change.
| Halves | Quarters | Eighths |
|---|
| 12 | 24 | 48 |
| 22 = 1 | 44 = 1 | 88 = 1 |
Find the missing number: 23 = ?6
- Look at the denominators: 3 has become 6. That is 3 × 2.
- Do the same to the numerator: 2 × 2 = 4.
- So 23 = 46.
Common mistake: adding the same number to the top and bottom. 12 does not equal 23 — one half is less than two thirds. You must multiply (or divide) both parts by the same number.
Adding fractions with the same denominator
When the denominators are the same, the pieces are the same size, so you just count them: 14 + 24 = 34. If the answer is a whole, say so: 34 + 14 = 44 = 1. A number like 112 (one and a half) is called a mixed number.
Check yourself
- A chocolate bar has 5 equal pieces and you eat 2. What fraction did you eat?
- 12 = ?8
- 34 = ?12
- Is 26 equivalent to 13?
- 25 + 25 = ?
- How many quarters make 2 wholes?
Answers: 1. 25 2. 4 3. 9 4. Yes (divide the top and bottom of 26 by 2) 5. 45 6. 8