Question 122043
Young's rule is a method to convert adult dosage of medicine for children. 

Let N= child's age,
D is the adult dosage of a medicine, 
C is the corresponding children's dosage of the medicine

{{{C = D/((N+12)/N)}}}

As an example, if the adult dosage is 100mg and the child is 8 years old, then
{{{C = D/((N+12)/N)}}}
{{{C = 100/((10+12)/10)}}}
{{{C = 1000/22}}}
{{{C = 45.5}}}
The 10 year old child's dose would be approximately 45 mg.

Remember always check the label for appropriate dosage and age limits with any medicines.