What would happen if we didnt use units when measuring?

"For a measurement to make sense, it requires both a number and a unit. For example, if you told one of your friends that you had finished a homework assignment "in five", what would your friend think? Would it be five minutes or 5 hours? Maybe it was a long assignment, and you actually meant 5 days. Or maybe you meant that you wrote 5 pages. You should always express measurements in numbers and units so that their meaning is clear."

Pearson Physical Science Concepts in Action, Chapter one page 16

a and c

c is 100% but i am confused in a

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form