SOLUTION: Please help me with the following word problem, I can not do percentages at all and I can not figure out the answer. Thank you so much! A chemist wants to mix a 5% alcohol solutio

Click here to see ALL problems on Systems-of-equations

Question 209326: Please help me with the following word problem, I can not do percentages at all and I can not figure out the answer. Thank you so much! A chemist wants to mix a 5% alcohol solution with a 25% alcohol solution to obtain 8 liters of a 20% alcohol solution. How much (in liters) of the 25% solution should she use?
Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website!
What might help you is to always
remember that percent means
"per one-hundred", so whenever
you see %, you must divide by
100.
------------------------------
A good question to ask with this
problem is: "How much water and
how much alcohol end up in the
final solution?
------------------------------
Let = liters of the 5% solution added
Let = liters of the 25% solution added
------------------------------
The equation to solve in words is:
(alcohol in 5% solution)+(alcohol in 25% soltion)/(alcohol + water in 20% solution) = 20%
So, I can write:
(1)
(2)
Multiply both sides of (1) by
(1)
(1)
Multiply both sides of (2) by and subtract from (1)
(2)
(2)
And, subtracting:
(1)
(2)

She should use 6 liters of the 25% solution
check answer:
(2)

Go back to (1)
(1)

It always helps if you can sum up the problem in
an equation with words like I did (It helps me a lot)