Chapter 4.3, Problem 1TU

TEST YOUR UNDERSTANDING | FOR EXAMPLE $4.7$

The salinity of a saltwater aquarium is being raised to a target value of $32$ parts per thousand of dissolved solids in the tank. The table below shows the difference $D$ between the target salinity and the current salinity $S$ after $t\text{hours}$. Both $D$ and $S$ are measured in parts per thousand.

$t=timeinhours$	$0$	$1$	$2$	$3$	$4$
$D=salinitydifference$	$32$	$25.60$	$20.48$	$16.38$	$13.11$

Make a model of $D$ as an exponential function of $t$. Find a formula that gives the salinity $S$ as s function of $t$.