Page 72 - Math Course 3 (Book 1)

Exponential Growth and Decay

Compound Interest
POPULATION

In 2005 the town of Flat Creek had Example
a population of about 280,000 and
a growth rate of 0.85% per year.
According to the equation, what will be the COLLEGE
population of Flat Creek in the year 2015? When Jing May was born, her grandparents
invested $1000 in a fixed rate savings account at
In 2015, t will equal 2015 – 2005 or 10. a rate of 7% compounded annually. The money will
t
y = 280,000(1.0085) Equation for population of go to Jing May when she turns 18 to help with her
Flat Creek college expenses. What amount of money will Jing
May receive from the investment?
10
y = 280,000(1.0085) t = 10
r
A = P(1 + ) nt Compound interest
y ≈ 304,731 Use a calculator. n equation.
0.07 P = 1000, r = 7% or 0.07,
A = 1000(1 + ) 1(18)
In 2015, there will be about 1 n = 1, and t = 18
Answer
304,731 people in Flat Creek.
A = 1000(1.07) 18 Compound interest
equation.

Your Turn! A = 3379.93 Simplify.

Exponential Growth Answer She will receive about $3380.
POPULATION
In 2000, Scioto School District had a student
population of about 4500 students, and a growth
rate of about 0.15% per year. Write an equation Compound Interest
to represent the student population of the Scioto
School District since the year 2000. COMPOUND INTEREST
When Lucy was 10 years old, her father invested
A. y = 4500(1.0015) $2500 in a fixed rate savings account at a rate
B. y = 4500(1.0015) t of 8% compounded semiannually. When Lucy
C. y = 4500(0.0015) t turns 18, the money will help to buy her a car.
D. y = (1.0015) t What amount of money will Lucy receive from the
investment?

Answer A. about $4682
B. about $5000
C. about $4600
POPULATION D. about $4500
In 2000, Scioto School District had a student
population of about 4500 students, and a growth Answer
rate of about 0.15% per year. According to the
equation, what will be the student population of
the Scioto School District in the year 2006?

A. about 9000 students
B. about 4600 students
C. about 4540 students
D. about 4700 students

Answer

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