Intermediate Algebra

Question

Fred is working at a forensics lab and needs 3 liters of an 8% HC1 solution to test some evidence. Fred has only a 5% solution and a 20% solution available to him. He needs to mix these solutions in order to obtain his 8% solution. How much of each should he use?

Answer 1

Use a weighted average: Let x = amount of 5% solution and y = amount of 20% solution

then (5x + 20y)/(x + y) = 8 and x + y = 3

So,

5x + 20y = 24

and x + y = 3

Solving the two equations we get x = 12/5 liters of the 5% solution

and y = 3/5 liters of the 20% solution