Evaluating formulas

# Evaluating formulas

Before you start there are some simple formulas to evaluate on page 5.

#### Question 1

A rule to calculate the amount of medicine (mL) a child needs is:

Child amount = (Adult amount × Age of child) ÷ (Age of child + 12)

(mL)
Age of child
(years)
Child amount
(mL)
10 8

#### Solution

Substitute in the formula. This formula is known as Young's rule and uses age to calculate the dosage.

 Child amount = (10 × 8) ÷ (8 + 12)(Evaluate the brackets first.) = 80 ÷ 20 = 4 mL.