Pharmacy Council Exam question no 1

The dose of a drug is 5mg /kg body weight. how much of the drug is required for a boy of 12 year who weighs 21kg

a. 1.5mg

b. 2.0mg

c. 2.5mg

d. 3mg

Use youngs formula : Adult Dose X (Age ÷ (Age+12)) = Child's Dose

 ans:- 2.5