You need a 60% alcohol solution. On hand, you have a 225 mL of a 50% alcohol mixture. You also have 85% alcohol mixture. How much of the 85% mixture will you need to add to obtain the desired solution?

90 ml

Step-by-step explanation:

225 ml of 50% solution contains:

225/2 = 112.5 ml of alcohol and same amount of water

x ml of 85% alcohol mixture contains

0.85x ml of alcohol and 0.15x of water

we need 60% solution which will contain:

(225+x) * 0.6 = 112.5+0.85x 135+0.6x = 112.5+0.85x 0.85x-0.6x = 135-112.5 0.25x = 22.5 x=22.5/0.25 x = 90 ml

so we require 90 ml of 85% solution added