Chapter 11.1, Problem 30PPS

To determine

To Find: $x$ when $y=-5$

Answer to Problem 30PPS

  $x=-11.2$

Explanation of Solution

Given: Assume that $y$ varies inversely as $x$ and $y=4$ when $x=14$

Given: $y=4$ when $x=14$

Product rule for Inverse variation

  $x_1{y}_1=x_2{y}_2$

Here

  $\begin{array}{l}{x}_1=14\\ y_1=4\\ x_2=?\\ y_2=-5\end{array}$

Then

  $\begin{array}{l}{x}_1{y}_1=x_2{y}_2\\ (14)(4)=(x_2)(-5)\\ 56=-5x_2\\ x_2=\frac{56}{-5}\\ x_2=-11.2\end{array}$

So, when $y=-5$ , $x=-11.2$