Evaluating formulas

Solution to question 1 continued

The formula could be written as

Child amount	= Adult amount × \(\dfrac{\text{Age of child}}{\text{Age of child}\,+\,12}\)
	= 10 × \(\dfrac{8}{8+12}\)
	= 10 × \(\dfrac{8}{20}\)
	= 10 × \(\dfrac{2}{5}\)
	= 4 mL.

\(\dfrac{2}{5}\) = 0.4 can be considered as a proportion. This increases as the age of the child increases. Notice that the formula suggests that an 18-year-old should get 6 mL but an 18-year-old is an adult. These results are summarised in the table and graph below.

Table 1. The results for an adult amount of 10 mL

Age of child (years)	Proportion	Adult amount (mL)	Child amount (mL)
4	0.25	10	2.5
6	\(0.\dot{3}\)	10	\(3.\dot{3}\)
8	0.4	10	4
12	0.5	10	5
18	0.6	10	6

Child amount (mL) against Age of child (years) for an adult amount of 10 mL

Detailed description of graph

Solution to question 1 continued

Question 2