need help please....?

Question

how much salt should you add to an 8 oz glass of water to make a 10% solution for a mouth rinse? please show and explain the answer...our teacher told us that the answer is in fraction..

Answer 1

let needed salt be x oz
Then
x/(x+8)=10/100

10x=x+8
9x=8

x=8/9 oz

As you see the answer is in a fraction form.

Answer 2

It's usually by weight. So 8 oz. x .01 = .08 oz. (salt). In fraction that would be 8/100 or 2/25. But why it would be expressed as a fraction, I don't know.