SOLUTION: A chemist has a 30% saline solution and a 55% saline solution available. How many milliliters of each of these available solutions should she mix to obtain 700 ml of a 40% solution

Question 402183: A chemist has a 30% saline solution and a 55% saline solution available. How many milliliters of each of these available solutions should she mix to obtain 700 ml of a 40% solution?
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
A chemist has a 30% saline solution and a 55% saline solution available. How many milliliters of each of these available solutions should she mix to obtain 700 ml of a 40% solution?
.
Let x = amount (ml) of 30% solution
then
700-x = amount (ml) of 55% solution
.
.30x + .55(700-x) = .40(700)
.30x + 385 - .55x = 280
385 - .25x = 280
-.25x = -105
x = 420 ml (30% saline)
.
55% saline:
700-x = 700-420 = 280 ml

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