Answer:
40mL of glycerol are needed to make a 20% v/v solution
Explanation:
This problem can be solved with a simple rule of three:
20% v/v is a sort of concentration. In this case, 20 mL of solute are contained in 100 mL of solution.
Therefore, in 100 mL of solution you have 20 mL of solvent (glycerol)
In 200 mL, you would have, (200 .20)/ 100 = 40 mL
