MathVine

To take a ratio and turn it into a fraction, you need to first work out the denominator. This is the number at the bottom of the fraction. In the fraction $rac{1}{3}$, 3 is the denominator.

To do this, you add the two numbers in the ratio together. Let's use the example from the introduction above, where we have a class with a ratio of 5:7 boys to girls (for every 5 boys, there are 7 girls).

We add the two numbers together:

$5 + 7 = 12$

Therefore, our denominator needs to be 12.

Then, we can just use the numbers from the ratio as our numerators (the top number of the fraction).

So $rac{5}{12}$ of the class are boys, and $rac{7}{12}$ are girls.

To test it, let's plug in some numbers. Let's imagine there is a total of 24 students in the class. To use the fractions, we would work out $rac{5}{12}$ of 24. That gives us 10 ($rac{5}{12} * 24 = 10$). To work out how many girls, we do $rac{7}{12} * 24$, which equals 14.

Since we have 10 boys and 14 girls the ratio is:

$10 : 14$

By making the ratio as simple as possible (dividing by 2), we get the ratio:

$5 : 7$

Therefore the fractions match the ratio and vice versa.