HOW MANY OUNCES OF EACH SOLUTION SHOULD SHE USE?

Question

A scientist has two solutions, which she has labeled Solution A and Solution B. Each contains salt. She knows that Solution A is
60%
salt and Solution B is
85%
salt. She wants to obtain
90
ounces of a mixture that is
80%
salt. How many ounces of each solution should she use?

Answer 1

Let x = the number of ounces of 60% salt

Let y = the number of ounces of 85% salt

 

x + y = 90   x = 90 - y (Equation #1)

.6x + .85y = .8(90) = 72  Multiply this whole equation by 100

60x + 85y = 7200   (Equation #2)

Substitute Eq. 1 into Eq. 2

60(90-y) + 85y = 7200

5400 - 60y + 85y = 7200

25y = 1800

y = 72 ounces

x = 90 - 72

x = 18 ounces