Chapter 4.3, Problem 3TU

TEST YOUR UNDERSTANDING | FOR EXAMPLE $4.9$

A radioactive substance is decaying. The amount $A$, in $\text{grams}$, present after $t\text{years}$ is given in the table below.

$t=years$	$0$	$10$	$20$	$30$	$40$
$A=amount$	$500.00$	$300.00$	$180.00$	$108.00$	$64.80$

Find a formula that gives $A$ as an exponential function of $t$.