MIXTURE PROBLEM. A pot contains 6L of brine at a concentration of 120g/L. How much of the water should be boiled off to increase the concentration to 200g/L?
Brine is water with salt dissolved in it.
Since there are 6L of the 120g/L brine, there are 6L×130g/L = 780 grams
of salt in those 6 liters of brine.
Let x = the number of liters of water needed so that those 780 grams of salt
would give it a concentration of 200g/L
780 grams of salt is to x liters of water as 200 grams is to 1 liter of water:
=
200x = 780
x =
x = 3.9 liters of solution.
Therefore we must reduce the 6L down to 3.9L.
Therefore 6L - 3.9L = 2.1 liters of water must be boiled off.
Answer: 2.1L
Edwin