Formula word problem

Question

Use Young's Rule to find the difference in a child's dosage for a 12-year-old child and a 4-year-old child. Express the answer as a single rational (or fractional) expression in terms of D. 

 

Young's Rule is: 

C=DA  

   A+12

 

 

 

 

( answer is 1/4 D but i need how step by step on how they got this answer)

Answer 1

Young's Rule as given in your problem is misstated. Furthermore, there is no starting point in your information. We need the adult dose, and the age of the child.  Here is the actual definition, and an example.

 

Young's Rule : Adult Dose x [Age ÷ (Age+12)] = Child's Dose

Example: 11 year old child; adult dose = 500mg
500mg x (11 ÷ (11+12)) = Child's Dose
500mg x (11 ÷ 23) = Child's Dose
500mg x .48 = Child's Dose
240mg= Child's Dose