Math Problem. again.

Question

You need a 20% alcohol solution. On hand, you have a 220 mL of a 60% alcohol mixture. How much pure water will you need to add to obtain the desired solution

Answer 1

pure water is 0% alcohol solution

It's 20% from 20%, while 60% is 40% from 20%. twice as far away

you need twice as much water or 2x220 = 440ml

60(220) + 0(x) = 20(220+x)

13200 = 4400+20x

20x = 13200-4400 = 8800

x = 8800/20 = 440 ml