1. Janie’s bank pays 2.8% annual interest compounded continuously on savings accounts. She placed $3000 in the account. How much money will be in Janie’s account 4 years after she made her deposit? Assume that she makes not additional deposits and no withdrawals.
Problem of the Day

2. Section 7-8 Using Exponential and Logarithmic Functions

3. Then Now Objectives You used exponential growth and decay formulas.
Use logarithms to solve problems involving exponential growth and decay.

4. Common Core State Standards
Content Standards
F.IF.8.b – Use the properties of exponents to interpret expressions for exponential functions.
Mathematical Practices
1) Make sense of problems and persevere in solving them.
Common Core State Standards

6. The half-life of a radioactive substance is the time it takes for half of the atoms of the substance to disintegrate.
Vocabulary

7. The half-life of Plutonium-239 is 24,000 years
The half-life of Plutonium-239 is 24,000 years. Determine the value of k and the equation of decay for Plutonium-239.
Example 1

8. The half-life of Sodium-22 is 2. 6 years
The half-life of Sodium-22 is 2.6 years. Determine the value of k and the equation of decay for Sodium-22.
Example 1

9. A geologist examining a meteorite estimates that it contains only about 10% as much Sodium-22 as it would have contained when it reached Earth’s surface. How long ago did the meteorite reach the surface of Earth?
Example 2

10. A paleontologist examining the bones of a prehistoric animal estimates that they contain 2% as much Carbon-14 as they would have contained when the animal was alive. How long ago did the animal live?
Example 2

11. A paleontologist examining the bones of a prehistoric animal estimates that they contain 2% as much Carbon-14 as they would have contained when the animal was alive. If prior research points to the animal being around 20,000 years old, how much Carbon-14 should be in the animal?
Example 2

12. p.513 #1, 4, 23 – 25
Homework

13. A radioactive element decays exponentially according to the equation 𝑦=𝑎 𝑒 − 𝑡 , where t is in days. Find the half-life of this element.
Problem of the Day