How many oz of the 14% acid solution should be in the mixture?

Question

A chemist needs to prepare 28 oz of a 9% hydrochloride acid solution. Find the amount of 14% solution and the amount of 7% solution she should mix to get this solution .

Answer 1

X+y = 28

0.14x + 0.07y = 28*0.09 = 2.52

0.14x + 0.07 ( 28 - x) = 2.52

0.14x + 1.96 - 0.07x = 2.52

0.07x + 1.96 = 2.52

0.07x = 0.56

7x = 56

x=8

y=20

0.14*8 + 0.07*20 = 1.12 + 1.4 = 2.52 = 28 * 0.09 <--- yes it checks

8 oz of the 14% solution and 20 oz of the 7% solution