A glucose solution that is prepared for a patient should have a concentration of 180 g/L. A nurse has 18 g of glucose. How many liters of water should she add to the glucose to obtain the required solution?

You start by using proportions to find the number of liters of solution:

180 g of glucose / 1 liter of solution = 18 g of glucose / x liter of solution

=> x = 18 g of glucose * 1 liter of solution / 180 g of glucose = 0.1 liter of solution.

If you assume that the 18 grams of glucose does not apport volume to the solution but that the volume of the solution is the same volumen of water added (which is the best assumption you can do given that you do not know the how much the 18 g of glucose affect the volume of the solution) then you should add 0.1 liter of water.

Answer: 0.1 liter of water.