Answer
Water temperature at a depth of 5000 meters is $0.88{}^\circ C$.
Work Step by Step
We are given that $t\propto \frac{1}{d}$.
Using the constant of proportionality we have, $t=\frac{k}{d}$, where t is the water temperature, d is depth of water and k is constant.
Now calculate the value of k according to the provided values,
$\begin{align}
& 4.4=\frac{k}{1000} \\
& k=4400
\end{align}$
Now, substitute $k=4400$ and $d=\text{ }5000$ in the expression $t=\frac{k}{d}$,
$\begin{align}
& t=\frac{4400}{5000} \\
& \ \ =0.88{}^\circ C
\end{align}$
Therefore, the water temperature at a depth of 5000 meters is $0.88{}^\circ C$.
