How many liters of a 10% alcohol solution must be mixed with 30 liters of a 50% solution to get a 20% solution?
Unknown amount at 10% = x
Unknown final amount = 30 + x
(percentage x amount) + (percentage x amount) = (final percentage x final amount)
0.10 · x + 0.50 · 30 = 0.20 · (x + 30)
0.10x + 15.00 = 0.20x + 6.00
0.10x + 9.00 = 0.20x
9.00 = 0.10x
90.0 = x
