Question

What is the rate of change of the water level , in feet per hour

Answer 1

A; rate of change is the same as slope, so, using the slope formula, $m= \frac{y_{2} - y\1_{1} }{ x_{2} - x_{1} }$, where $m$ is the slope and $x_{1}$, $x_{2}$, $y_{1}$, and $y_{2}$ are the $x$ and $y$ values.

Plug in $2$ points for $x$ and $y$, water level being the $y$ and time being the $x$ since we're looking for the answer in ft/hr-- you can choose any two, but from the same row.

$m= \frac{ 30-50}{4-0}$
$m= \frac{-20}{4}$
$m= \frac{-5}{1}$
$m= -5$ ft/hr