Question

How many ounces of a 30% alcohol solution must be mixed with 9 ounces of a 35% alcohol solution to make a 31% alcohol solution ?

Answer 1

36 ounces

Explanation:

Let q represent the quantity of 30% solution required. The total amount of alcohol in the mix is ...

30%·q + 35%·9 = 31%·(q +9)

30q + 315 = 31q +279 . . . . multiply by 100 and eliminate parentheses

36 = q . . . . . add -(279+30q) to both sides

36 ounces of 30% alcohol must be mixed to make the 31% solution.