Expressing a Fraction in its Lowest Terms

We have already seen that the same fraction can be written in a number of different ways.
e.g. 1/2 = 10/20

Usually we want to express a fraction in its simplest form.

i.e. with both numerator and denominator having the smallest possible numbers.

This is known as writing a fraction in its lowest terms.

It is sometimes called cancelling.

Worked example

Question

Write the following fraction in its lowest terms

15

20

Answer

1. Look at the numerator and the denominator.
   
2. Find a number which divides into both (in this case it is 5).
   
3. Divide both the top and bottom by this number.

15	=	3
20		4

Sometimes you may need to repeat the process.