The situation can be represented by the following equation: [tex]z=\frac{k}{xy}[/tex] where k is a constant of proportionality. Plugging in the given values: [tex]0.5=\frac{k}{2\times4}[/tex] from which k = 4. When x = 4 and y = 9 [tex]z=\frac{4}{4\times9}=\frac{1}{9}[/tex]
