1. UNIT 5: EXPONENTIAL GROWTH AND DECAY CONTINUOUS Exponential Growth and Decay Percent of change is continuously occurring during the period of time (yearly, monthly, …) Examples: “Continuous Interest”, “Radioactive Half-Life” y = final amount a = original amount k = growth rate constant t = time + = Growth, - = Decay

2. Example 1Continuous Exponential Growth b)Jill invested $1000 into a CD account that claims to compound continuously at 10%. How long will it take triple her investment? a)A population of rabbits is growing continuously at 20% each month. If the colony began with 2 rabbits, how many months until they reach 10,000 rabbits? 42.6 months 11.0 years c) The population of Raleigh was 212,000 in 1990 and was 259,000 in 1998. Write a continuous exponential growth equation, where t is the numbers of years after 1990 for Raleigh’s population.

3. Example 2Continuous Exponential Decay a)A paleontologist finds the bones of a Wooly Mammoth. She estimates the bones only contain 4% of the Carbon-14 that it would have had alive. Estimate the age of the Mammoth. 26,824.0 years old #1: The formula for the half life of Carbon-14 The half-life of Carbon-14 is 5760 years which means that every 5760 years half of the mass decays away. 1b) A paleontologist finds that the Carbon-14 of a bone is 1 / 12 of that found in living bone tissue. What is the age of the bone?

4. #2: The half life of Sodium-22 is given below. A geologist is studying a meteorite and estimates that it contains only 12% of as much Sodium-22 as it would have when it reached the earths atmosphere. How long ago did the meteorite reach earth. 8.0 years old #3: Radioactive iodine decays according to the equation, where t is in days. Find the half-life of the substance. #4: The half life of Radium-226 is 1800 years. Find the half-life equation for Radium-226.