Introducing fractions

If you get {7} out of {10} in a test, you can write your score as \frac{7}{10}.

{7} expressed as a fraction of {10} is \frac{7}{10}.

Similarly, if there are {20} socks in a drawer and {4} of them are blue, \frac{4}{20} of the socks are blue.

{4} expressed as a fraction of {20} is \frac{4}{20}. We can put this into its simplest form by dividing the top and bottom numbers by {4}, so we get \frac{1}{5}.

Question
3 shaded squares and 10 shaded squares

a) What fraction of the large shape is the small one?

b) What fraction of the small shape is the large one?

a) The small shape is \frac{3}{10} of the large shape.

b) The large shape is \frac{10}{3} or {3}\frac{1}{3} of the small shape.

curriculum-key-fact
If you are expressing a number as a fraction of a second number, the first number goes on the top and the second number on the bottom.
Question

What fraction of {1} metre is {42}~cm? Give your answer in its simplest form.

{42}~cm as a fraction of {100}~cm is:

\frac{42}{100}=\frac{21}{50}