1. Applications of Exponential Functions
Section 3.1B
Applications of Exponential Functions
Formulas for Compound Interest
After t years, the balance A in an account with principal P and annual interest rate r (in decimal form) is given by the following formulas:
1. For n compoundings per year:
2. For continuous compounding: A = Pert

2. Ex 8: A total of $9000 is invested at an annual interest. rate of 2
Ex 8: A total of $9000 is invested at an annual interest rate of 2.5%, compounded annually. Find the balance in the account after 5 years.
Ex 9: A total of $12,000 is invested at an annual interest rate of 3%. Find the balance after 4 years if the interest is compounded a) quarterly and b) continuously.
$10,182.67
a. $13,523.91
b. $13,529.96

3. Ex 10: Let y represent a mass of radioactive strontium,
Ex 10: Let y represent a mass of radioactive strontium, in grams, whose half-life is 28 years. The quantity of strontium present after t years is .
What is the initial mass (when t = 0)?
How much of the initial mass is present after 80 years?
10 grams
1.380 grams

4. Ex 11: The approximate number of fruit flies in an
Ex 11: The approximate number of fruit flies in an experimental population after t hours is given by Q(t) = 20e0.03t, where t ≥ 0.
Find the initial number of flies in the population.
How large is the population after 72 hours?
Graph Q.
20 flies
173 flies

6. Suggested Assignment:
S 3.1B pg #