Chapter 5.3, Problem 69MR

To determine

To write a direct variation equation that relates $x$ and $y$

The value of $y$ when $x=10$ .

Answer to Problem 69MR

Direct variation equation is $y=2x$ and $y=20$ when $x=10$ .

Explanation of Solution

Given:

  $y=8$ when $x=4$

Calculation:

Consider the direct variation equation as,

  $y=k\cdot x\to \left(1\right)$

Now put $y=8$ and $x=4$ in equation (1), we get

  $\begin{array}{l}8=k\cdot 4\\ \Rightarrow k=2\end{array}$

Therefore equation (1) becomes,

  $y=2x$

Now when $x=10$ ,

  $\begin{array}{l}y=2\left(10\right)\\ \Rightarrow y=20\end{array}$