<PRE><B>Question 936125</B>
let y = the number of gallons of 100% acid solution that you have to add to get a 50% acid solution.


you have 20 gallons of 20% acid solution.


your equation will be:


.2 * 20 + y = .5 * (20 + y)


20 + y is the total amount of gallons of solution that you will have when you are done.


simplify this equation to get:


4 + y = 10 + .5 * y


subtract .5 * y from both sides of this equation and subtract 4 from both sides of this equation to get:


y - .5 * y = 10 - 4


simplify to get:


.5 * y = 6


divide both sides of this equation by .5 to get:


y = 12


you will need 12 gallons of 100% acid solution added to 20 gallons of 20% acid solution to get 32 gallons of 50% acid.


the number of gallons of pure acid in the new solution will be .2 * 20 + 12 which is equal to 4 + 12 = 16


16 / 32 = 50%


numbers look good.


your solution is that you will need to add 12 gallons of 100% sulfuric acid to 20 gallons of 20% sulfuric acid to make 32 gallons of 50% sulfuric acid.


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