SOLUTION: One solution contains 50% alcohol and another solution contains 80% alcohol. How many liters of each solution should be mixed to produce 10.5 liters of a 70% alcohol solution?

Question 291550: One solution contains 50% alcohol and another solution contains 80% alcohol. How many liters of each solution should be mixed to produce 10.5 liters of a 70% alcohol solution?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = liters of 50% solution needed
Let = liters of 80% solution needed
In words:
(liters of alcohol in final solution)/(total liters of final solution)
= 70%
given:
alcohol in 50% solution:

alcohol is 80% solution:

and
(1)
(2)
----------------------
Multiply both sides of (1) by
(1)
Multiply both sides of (2) by
and subtract (2) from (1)
(1)
(2)

And from (2):

3.5 liters of 50% solution and 7 liters of 80% solution are needed
check answer:
(1)
(1)

OK
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