SOLUTION: A chemical manufacturer wishes to fill an order for 700 gallons of a 24% acid solution. Solutions of 20% and 30% are in stock. How many gallons of 20% acid solution will be used in

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Question 1097567: A chemical manufacturer wishes to fill an order for 700 gallons of a 24% acid solution. Solutions of 20% and 30% are in stock. How many gallons of 20% acid solution will be used in the desired mixture?
(I understand there may not be such a thing as "24% acid solution", et cetera. I'm just focusing on what solution needs to be used to get the number being asked for.
Honestly, I've seen problems like these before but just have trouble when it's worded differently. Thank you!)
Answer by Boreal(15235) (Show Source):
You can put this solution on YOUR website!
x=gallons of 20% acid
700-x=gallons of 30% acid
the pure acid in each is .20x+.30(700-x)=700*.24
.20x+210-.30x=168
-.10x=-42
x=420 gallons of 20%
700-x=280 gallons of 30%
The concept of pure acid is the per cent * volume
Also
24% is 4/10 of the way from 20 to 30, so 6/10 of the acid should be 20%. .6*700=420.