This activity is about keeping pairs of numbers in the same ratio.
If two quantities are in direct proportion, the ratio between corresponding values will always be the same.
| a | = | 1 | 2 | 3 | 4 | 5 |
| b | = | 1.5 | 3 | 4.5 | 6 | 7.5 |
In this table, the ratio between a and b can be found by dividing the value of b by its corresponding value of a.
Where B is 3 and A is 2: 3 ÷ 2 = 1.5
Where B is 4.5 and A is 3: 4.5 ÷ 3 = 1.5
Now we know that the ratio between a and b is 1.5
If we know a and we want to find b, we simply multiply a by 1.5
For example, if a = 6 then b = 1.5 × 6 = 9
We can also use this ratio to find the value of a if we know what b is.
We do the inverse and simply divide b by 1.5
For example if b = 15, then a = 15 ÷ 1.5 = 10
The best way to check that we've got this is to try some questions, so let's get started.
