Question

A scientist has two solutions, which she has labeled Solution A and Solution B. Each contains salt. She knows that Solution A is 65% salt and Solution B is 90% salt. She wants to obtain 120 ounces of a mixture that is 75% salt. How many ounces of each solution should she use?

Answer 1

• 48 oz of 90% (B)
• 72 oz of 65% (A)

Explanation:

The amount of salt in the mixture is the sum of the amounts of salt in the constituents. Those amounts are found by multiplying the quantity of solution by the percentage that is salt.

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Let x represent the quantity of 90% salt solution B, in ounces. Then the number of ounces of salt in the mix is ...

0.90x +0.65(120 -x) = 0.75(120)

0.25x = 0.10(120) . . . . . . subtract 0.65(120) and simplify

x = 48 . . . . . . . . . . . . . divide by 0.25

120 -x = 72 . . . . . . . amount of 65% solution A

She should use 48 ounces of 90% solution B, and 72 ounces of 65% solution A.