Answer
$\color{blue}{t=\dfrac{12}{\sqrt{x}}}$
Work Step by Step
$y$ varies inversely with $\sqrt{x}$, so the equation that represents the variation is:
$y=\dfrac{k}{\sqrt{x}}$
Since $y=4$ when $x=9$, substituting these into the tentative equation above gives:
$y=\dfrac{k}{\sqrt{x}}
\\4=\dfrac{k}{\sqrt{9}}
\\4=\dfrac{k}{3}
\\3(4) = \dfrac{k}{3} \cdot 3
\\12=k$
Thus, the equation of the inverse variation is:
$\color{blue}{t=\dfrac{12}{\sqrt{x}}}$
