100 : 80 =

100 : 80 can be simplified by dividing both numbers by 20.

So, 100 ÷ 20 = 5 and 80 ÷ 20 = 4.

Thus, 100 : 80 = 5 : 4.

Alternatively, you can express it as a decimal ratio by dividing 100 by 80, which gives:

100 ÷ 80 = 1.25.

So, the ratio can also be represented as 1.25 : 1.