Think of it like this. You can read 6 chapters of a book in 3/5 of an hour. How many chapters could you read in 1 hour?
When finding the unit rate, whatever you do on one side, you do on the other--just like in an equation. If you divide by 2 on one side, divide by 2 on the other. For example, if you have the ratio 4:2, if you divide 4 by 2, you also have to divide 2 by 2, to get the equivalent ratio (and unit rate) of 2:1.
Anyway, let's divide both sides of 6 : 3/5 by 3. 6 / 3 = 2. 3/5 / 3 = 1/5. (This is because there are 3 parts of 5 in 3/5, and 3 parts divided by 3 equals just 1 part, of 5, or 1/5.) So 2 : 1/5 is an equivalent ratio. You can read 2 chapters in 1/5 of an hour.
After this, it's easy. We know we need to find out how much to read in one hour, not one-fifth. So what do we multiply 1/5 by to get 1? 5! (Because 1/5 means one part of 5, and one part times 5 equals 5. 5 parts of 5 parts is a whole, or 1.) Of course, we have to multiply by the same for the other side: 2*5=10. So, our unit rate is 10:1. You can read 10 chapters in one hour!
10:1
