Chapter 4.2, Problem 21E

Reminder Round all answers to two decimal places unless otherwise indicated.

A Diet An overweight man makes lifestyle changes in order to lose weight. He currently weighs $260\text{ pounds}$, and he has set a target weight of $200\text{ pounds}$. Each month the difference $D$, in pounds, between his current weight and his target weight decreases by $10\%$.

a.	Make an exponential model of $D$ versus the time $t$ in months since the diet began.
b.	How long will it take for his weight to reach $210\text{ pounds}$