IXL - Exponential growth and decay: word problems (Algebra 1 practice)

Colette has an exterminator visit regularly to control an ongoing cockroach problem. It's been working, and the population has declined by

15%

every year. If the population is currently 3,800 cockroaches, how many will there be in 3 years?

If necessary, round your answer to the nearest whole number.

cockroaches

ref_doc_title.

Learn with an example

question

Joel has a vintage comic book worth $360. According to a dealer, the value of this particular comic book will increase by

each year. How much will the comic book be worth in 15 years?

If necessary, round your answer to the nearest cent.

key idea

This is the formula for exponential growth:

(

)

In this formula,

is the initial amount,

is the rate of increase expressed as a decimal,

is the elapsed time, and

is the final amount.

solution

Plug in $360 for the initial amount, 0.05 for the rate of increase, and 15 years for the time elapsed.

(

)

Plug in values

360

(

0.05

)

Plug in values

Add

360

(

1.05

)

Add

Simplify

360

(

2.07892…

)

Simplify

Multiply

748.41414…

Multiply

Round to the nearest cent.

748.41414… → 748.41

To the nearest cent, Joel's comic book will be worth $748.41.

Looking for more? Try these:

Lesson: Exponential growth

Lesson: Exponential decay

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Teacher tools

Work it out

Not feeling ready yet? These can help:

V.1Evaluate an exponential function

CC.7Multiply a decimal by a multi-digit whole number

Lesson: Exponential growth

Lesson: Exponential decay

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