Answer:
40 mg
Step-by-step explanation:
Given,
The prescribed dosage the medicine for an adult = 180 milligrams,
Since, the minimum age of an adult = 18 years,
So, the prescribed dosage of the medicine for 18 years old person = 180 milligrams,
Thus, the ratio of prescribed dosage of medicine ( in mg ) and age of person ( in years ) =
Suppose prescribed dosage of a certain medicine for a child 4 years old is x mg,
So, ratio of prescribed dosage of medicine and age =
Hence, the prescribed dosage of a certain medicine for a child 4 years old would be 40 mg.