Ratio tables
You learn to fill in a ratio table by multiplying the top and the bottom by the same number.
How to work it out
- Find how many times larger the top number gets: 2 becomes 6 (times 3).
- Multiply the bottom number by 3 as well.
2
6
3
9
A worked example
Top: 1 and 3. Bottom: 2 and ?
- Find the factor on top: 1 × 3 = 3, so times 3.
- Do times 3 underneath too: 2 × 3 = 6.
- It goes with 6.
1
3
2
6
More examples
Top: 2 and 6. Bottom: 3 and ?
- Find the factor on top: 2 × 3 = 6, so times 3.
- Do times 3 underneath too: 3 × 3 = 9.
- It goes with 9.
Top: 3 and 12. Bottom: 5 and ?
- Find the factor on top: 3 × 4 = 12, so times 4.
- Do times 4 underneath too: 5 × 4 = 20.
- It goes with 20.
3
12
5
20
Watch out
You add instead of multiplying: on top 2 becomes 6, so underneath you do 3 + 4 = 7.
Look at how many times bigger it gets, not how much you add. 2 to 6 is times 3, so underneath 3 × 3 = 9.
Tips
- Draw an arrow between the numbers and write the step on it, like "times 3".
Why it works
In a ratio table the numbers on top and underneath go together, like 2 packs and 3 pounds. If you take 3 times as many packs, you pay 3 times as much. That is why you always multiply underneath by the same number as on top.