SOLUTION: how many ounces of water must be evaporated from 50oz of a 12% salt solution to produce a 15% salt solution? I know that the answer is 10oz, however i do not know how the book got

Question 519782: how many ounces of water must be evaporated from 50oz of a 12% salt solution to produce a 15% salt solution? I know that the answer is 10oz, however i do not know how the book got that as the answer. my teacher is using a 3 by 3 box set up to answer these word problems. I just cant figure this one out...
Answer by oberobic(2304) (Show Source): You can put this solution on YOUR website!
This is an interesting variation on a typical solution problem. The same rule of keeping track of how much 'pure' stuff still applies, but in this case we are evaporating water to increase the salt concentration.
.
You have 50 oz of 12% salt solution. That means have .12*50 = 6.0 oz of pure salt.
.
You need to produce 15% salt solution.
So 6 oz of pure salt = 15% of how much?
.
.15x = 6
x = 6/.15
x = 40
.
That means that if you have 40 oz of solution containing 6 oz of pure salt, you have a 15% solution.
You can check this by dividing 6/40 = .15
.15 * 100 = 15%
Correct.
.
You have 50 oz of solution now, and you need 40 oz of solution, so you need to evaporate 10 oz of water.
.
Done.
RELATED QUESTIONS
how much water must be evaporated from 300 ounces of 12% salt solution to obtain a 15%... (answered by Alan3354)

how much water must be evaporated from 32 ounces of a 4% salt solution to produce a 6%... (answered by Earlsdon)

How many ounces of water must be evaporated from 135 ounces of a 10% salt solution to... (answered by ewatrrr)

How much water must be evaporated from 32 ounces of a 4% salt solution to make a 7% salt... (answered by ptaylor)

How much water must be evaporated from 32 ounces of a 4% salt solution to make a 6% salt... (answered by ptaylor)

how much water must be evaporated from 28 ounces of a 3% salt solution to make a 7% salt... (answered by stanbon)

How much water must be evaporated from 32 ounces of a 4% salt solution to make a 6% salt... (answered by ankor@dixie-net.com)

How much water must be evaporated from 32 ounces of a 5% salt solution to make a 8% salt... (answered by ptaylor)

How much water must be evaporated from 28 ounces of a 5% salt solution to make a 7% salt... (answered by josmiceli)