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.
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.