Question 12470
Let's see, 32 oz of 4% salt solution is 96% water and 6% salt solution is 94% water. Since we are not removing any salt, the question can be rephrased: How much water must be evaporated from 32 oz of 96% water solution to produce a 94% water solution? Change the percentages to decimals.  94% = 0.94, 96% = 0.96, 100% = 1

The equation is now in terms of water rather than salt:

{{{32(0.96) - x(1) = (32-x)(0.94)}}}

{{{30.72 - x = 30.08 - 0.94x}}} Subtract 30.08 from both sides.

{{{0.64 - x = -0.94x}}} Add x to both sides.

{{{0.64 = 0.06x}}} Divide both sides by 0.06

{{{x = 0.64/0.06}}}

{{{x = 10.67}}}

So, 10.67 oz of water must be evaporated. This is one third of the original 32 oz. of solution.