Let's suppose that we have 8 red coins and 4 blue coins.


The ratio of the number of red coins to the number of blue coins is 8: 4.

Now, let's rearrange the coins into stacks of 2 coins each as shown below.


Now, the ratio of the number of red coins to the number of blue coins is 4 : 2.

Finally, let's put the coins into stacks of 2 coins each as shown below.


The new ratio of the number of red coins to the number of blue coins is 2 : 1.

For every 8 red coins there are 4 blue coins.

       Or

For every 4 red coins there are 2 blue coins.

       Or

For every 2 red coins there is 1 blue coin.


The ratios 8 : 4, 4 :2 and 2 : 1 are, therefore, equivalent ratios.

2:1 is the simplest form of 8:4.