Question

x is inversely proportional to y, and x = 18 when y = 4. a. Write an equation relating x and y b. Find x when y = 30

Answer 1

$\begin{gathered} a)\text{ xy = 72} \\ b)\text{ x = 2.4} \end{gathered}$

Here, we want to solve a proportional relationship problem

a) We have the proportion as follows;

$\begin{gathered} x\propto\frac{1}{y} \\ \\ k\text{ as constant} \\ \\ k\text{ = xy} \\ \\ \text{for x = 18 and y = 4} \\ \\ k\text{ = 18}\times4\text{ = 72} \\ xy\text{ = 72} \end{gathered}$

b) X, when y = 30

$\begin{gathered} xy\text{ = 72} \\ x\text{ = }\frac{72}{y} \\ x\text{ = }\frac{72}{30} \\ x\text{ = 2.4} \end{gathered}$