Chapter 4.2, Problem 2TU

TEST YOUR UNDERSTANDING | FOR EXAMPLE $4.5$

There are $2000$ pounds of pollutant in a reservoir. The cleanup operation can remove $12\%$ of the pollutant each month. Find a formula that gives the amount $P$, in pounds, of pollutant remaining after $t\text{months}$. How long will it be until half the pollutant is gone?