Question

How much water should be added to 38mL of 20% alcohol solution to reduce the concentration to 19%?

Answer 1

2 mL

Explanation:

There's 38(0.20) = 7.6 mL of alcohol in the 38 mL solution. If we are reducing the concentration to 19%, then we need to determine 19% of what total solution gets you 7.6 mL:

0.19x = 7.6

x = 40

Therefore, because you need 40 mL of total solution, then we need to add 2 mL of water since 38 mL + 2 mL = 40 mL.