Doreen Schmidt is a chemist. She needs to prepare 32 ounces of a ​15% hydrochloric acid solution. Find the amount of ​16% solution and the amount of ​8% solution she should mix to get this solution.

Question

How many ounces of the ​16% acid solution should be in the​ mixture?

Answer 1

Let x is amount of 16% solution, then (32 - x) is amount of 8% solution.

We have: 0.16x + 0.08(32 - x) = 0.15·32; 0.16x + 2.56 - 0.08x = 4.8; 0.08x = 2.24, x = 2.24/0.08; x = 28

32 - x = 32 - 28 = 4.

Answer: 28 ounces of 16% and 4 ounces of 8% solution

Answer 2

8x + 16(32-x) = 15(32)

8x = 32

x =4 ounces of 8%

32-4 = 28 ounces of 16% to get 32 ounces of 15%

15 is much closer to 16 than to 8, so you know most of the mixture will be from 16%

16-15 = 1

15=8 = 7. It's 7 times farther away from 16. 28 is 7 times 4.