SOLUTION: How many gallons of a 30% hydrochloric acid solution and 80% hydrochloric acid solution must be mixed to get 20 gallons of a 50% hydrochloric acid solution. so far i have tried th

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Question 1000909: How many gallons of a 30% hydrochloric acid solution and 80% hydrochloric acid solution must be mixed to get 20 gallons of a 50% hydrochloric acid solution.
so far i have tried these two equations and than substituted:

30x+80y=50
x+y=20

and
.3x+.8y=.5
x+y=20
every time the answer end being (x=31,y=-11) as far as i see you cannot have a negative amount of the 80% solution. help...

Answer by Edwin McCravy(20056)   (Show Source): You can put this solution on YOUR website!
You are forgetting to multiply the 50% or .5 by the 20 gallons 
and you are only putting .5 instead of .5(20)

That is, you have this:

.3x+.8y=.5
x+y=20 

but you should have this:

.3x+.8y=.5(20)
x+y=20 

Now try it.

Edwin

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