Question

How do you write the fraction `9/21` in simplest form?

Answer 1

`3/7`

Explanation:

`9/21=(cancel(3)xx3)/(cancel(3)xx7)=3/7`

Answer 2

`3/7`

Explanation:

We have to find a `color(blue)"common factor"` that will divide into both 9 and 21 and reduce the fraction.

In this case the lowest common factor is `color(red)(3)`

`rArr9/21=(9÷3)/(21÷3)=3/7`

This is usually written as shown below.

`9/21=cancel(9)^3/cancel(21)^7=3/7larrcolor(red)" in simplest form"`

This process is called `color(blue)"cancelling"`

A fraction is in `color(red)"simplest form"` when no other factor apart from 1 will divide into the numerator/denominator.