SOLUTION: How many ounces of pure alcohol must be added to 40 ounces of a 70% alcohol solution to produce an 85% alcohol solution?

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Question 295596: How many ounces of pure alcohol must be added to 40 ounces of a 70% alcohol solution to produce an 85% alcohol solution?
Found 2 solutions by mananth, nerdybill:
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
How many ounces of pure alcohol must be added to 40 ounces of a 70% alcohol solution to produce an 85% alcohol solution?
let quantity of pure alcohol to be added be x ounces
70% alcohol is 40 ounces
the total will be x+40 ounces
x+0.7*40 = (x+40)*0.85
x+2.8 =0.85x +34
0.15x=34-2.8
0.15x=31.2
x=208

Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
How many ounces of pure alcohol must be added to 40 ounces of a 70% alcohol solution to produce an 85% alcohol solution?.
.
Let x = ounces of pure alcohol added
then
x + .70(40) = .85(40+x)
x + 28 = 34 + .85x
.15x + 28 = 34
.15x = 6
x = 6/.15
x = 40 ounces