Question 1156014

How many liters of a 70% alcohol solution must be added to 50 liters of a 40% alcohol solution to produce a 50% alcohol solution?
<pre>Let amount of 70% solution be S
Then we get: .7S + .4(50) = .5(S + 50)
.7S + 20 = .5S + 25
.7S - .5S = 25 - 20
.2S = 5
S, or amount of 70% solution to mix, = {{{highlight_green(matrix(1,4, 5/.2, "=", 25, L))}}}