Answer: 3 mL
Explanation:
If a vial contains 15 mL of medicine, and each dose is 1/5 of the vial, you can calculate the size of each dose by dividing the total volume of the vial by the number of doses:
Size of each dose = Total volume of vial / Number of doses
Size of each dose = 15 mL / 5
Size of each dose = 3 mL
Each dose is 3 mL in size.