1. 4.9 Exponential and Log/Ln Word Problems Example: Given that population is growing exponentially with the function (this is based on historical data from 1992 to 2000): Assume Population (P) is in billions t is in years since 1990 When will the population reach 10 billion?

2. Carbon Dating The Radio-isotope Carbon 14 decays at a constant rate and thus can be used to determine the age of any Organic material, using the ratio of carbon 14 to carbon 12. This ratio is given by: The ratio of carbon 12 to carbon 14 in a newly discovered fossil is estimate the age of the fossil.

3. Spread of a Virus On a college campus of 5000 students, one student returns from a vacation with a contagious and long lasting flu virus. The spread of the virus is modeled by: a) After 5 days how many students are infected? b) Classes are canceled when the number infected is 40% or more. How many days will it take for this number to be reached?

4. Half Life and Doubling Time Half Life – time it takes for half the material to be gone due to decay/elimination of some kind. Doubling Time – time it takes for the material of any kind to double.

5. Half Life/Doubling Time Example: 200 grams of radium are stored in a container. The amount R(in grams) of Radium present after t years can be modeled by: What is the half life of Radium?