Question

Find the constant of proportionality, then write an equation relating x and yy is directly proportional to x, and y = 81 when x = 9

Answer 1

When x=9, y=81.

To find the proportionality constant take the ratio of y/x.

$\begin{gathered} \frac{y}{x}=\frac{81}{9} \\ =9 \end{gathered}$

Thus, the proportionality constant is 9.

The relation between y and x can be determined as,

$\begin{gathered} \frac{y}{x}=constant \\ \frac{y}{x}=9 \\ y=9x \end{gathered}$

Thus, the required relationship between x and y is y=9x.