SOLUTION: How many liters of a 30% alcohol solution do you need to mix with 50 liters of a 60% soultion to obtain a 35% solution?

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Question 13607: How many liters of a 30% alcohol solution do you need to mix with 50 liters of a 60% soultion to obtain a 35% solution?
Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
think of "before" and "after"

before --> got 50 litres of 60% and x litres of 30%.
after --> got (50+x) litres of 35%.

Just looking at this, the final solution is very close to the 30% solution, so there must be a lot of the 30%, to "drag" the concentration down from 60%. So i am looking for a common sense answer that is a lot more than 50 litres.

So,
(50*0.60) + (x*0.30) = (50+x)*0.35
30 + 0.3x = 17.5 + 0.35x
0.05x = 12.5
--> x = 250 litres.

jon.