In order to find a unit rate, the second part of the ratio must equal one. For example, let's say we want to find the ratio of 10/5. The second part of the ratio is 5. To get from 5 to 1, we must divide by 5. 5 / 5 = 1. However, what you do to the second part, you do to the first part. 10 / 5 = 2. The unit rate is 2:1.
