If the order is for 250 mL of medication and you have a 500 mL bag, what fraction of the bag is to be used?

To determine what fraction of the 500 mL bag is being used for the order of 250 mL, you can set up the problem by comparing the ordered amount to the total volume of the bag.

Since the total volume of the bag is 500 mL and the order is for 250 mL, you can find the fraction of the bag that is to be used by dividing the ordered amount by the total volume of the bag:

250 mL (ordered amount) ÷ 500 mL (total volume of the bag) = 0.5

This calculation shows that the medication ordered is half of the total volume of the bag. Therefore, the correct fraction of the bag that is to be used is 1/2, which corresponds to option C. This means that when you take 250 mL from a 500 mL bag, you are utilizing exactly half of that bag.