What is the unit rate for the ratio 6 : 3/5

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

The answer is 10:1 and the other person is correct

The answer would be c