The ratio compares two quantities (in this case blue and white parts).
A unit rate (or unit ratio) describes how many units of the first type of quantity corresponds to one unit of the second type of quantity. In our case the first type of quantity is blue parts and the second is white parts, so we should find how many blue parts correspond to one white part.
The ratio is: 5/4
We will obtain the unit ratio if we divide each number with 4 in order to get 1 - as a second quantity.
So, (5/4)/(4/4)= (5/4)/1
The unit ratio is:
(5/4)/1.
