Question

In the lab, Manuel has two solutions that contain alcohol and is mixing them with each other. Solution A is 50% alcohol and Solution B is 10% alcohol. He uses 1200 milliliters of solution A. How many milliliters of Solution B does he use if the resulting mixture is a 40% alcohol solution?

Answer 1

Suppose he uses x mls of solution B.
0.5*1200 +0.1x=0.4(1200+x)
600+0.1x=480+0.4x
0.3x=120
x=400