SOLUTION: How much of a 50% acid solution must be mixed with 50 gallons of a 12% acid solution to obtain a solution that is 40% acid? I tried to do 0.5X + 50(0.12)= 0.4, but I got a negat

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Question 651716: How much of a 50% acid solution must be mixed with 50 gallons of a 12% acid solution to obtain a solution that is 40% acid?
I tried to do 0.5X + 50(0.12)= 0.4, but I got a negative answer.
Found 2 solutions by nerdybill, ewatrrr:
Answer by nerdybill(7384) (Show Source):
You can put this solution on YOUR website!
How much of a 50% acid solution must be mixed with 50 gallons of a 12% acid solution to obtain a solution that is 40% acid?
.
Let x = amount (gallons) of 50% acid added
then
.50x + .12(50) = .40(x+50)
.50x + 6 = .40x+20
.10x + 6 = 20
.10x = 14
x = 14/.10
x = 140 gallons

Answer by ewatrrr(24785) (Show Source):
You can put this solution on YOUR website!

Hi,
Correct Set Up is:
0.5X + 50(0.12)= 0.4(X+50) ||The amount of 'solution' on both sides must be the same

X = 140gal of 50% solution needed
and..