SOLUTION: A chemist needs a saline solution that is 20% sodium chloride but only has solutions that are 15% and 40% sodium cholride. If the chemist measures 150mL of the 15% solution, how ma

Question 162791: A chemist needs a saline solution that is 20% sodium chloride but only has solutions that are 15% and 40% sodium cholride. If the chemist measures 150mL of the 15% solution, how many milliliters of the 40% solution should she add to make a 20% solution?
Answer by checkley77(12844) (Show Source): You can put this solution on YOUR website!
.40X+.15(150-X)=.20*150
.40X+22.5-.15X=30
.25X=30-22.5
.25X=7.5
X=7.5/.25
X=30 ML OF 40% SOLUTION IS USED.
150-30=120 ML OF 15% SOLUTION IS USED.
PROOF:
.40*30+.15*120=.20*150
12+18=30
30=30
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