Section 8.7 Exponential Growth and Decay
857
Version: Fall 2007
8.7
Exercises
1.
Suppose that the population of a cer
tain town grows at an annual rate of 6%.
If the population is currently 5
,
000, what
will it be in 7 years? Round your answer
to the nearest integer.
2.
Suppose that the population of a cer
tain town grows at an annual rate of 5%.
If the population is currently 2,000, how
many years will it take for it to double?
Round your answer to the nearest hun
dredth.
3.
Suppose that a certain radioactive
isotope has an annual decay rate of 7.2%.
How many years will it take for a 227
gram sample to decay to 93 grams? Round
your answer to the nearest hundredth.
4.
Suppose that a certain radioactive
isotope has an annual decay rate of 6.8%.
How many years will it take for a 399
gram sample to decay to 157 grams? Round
your answer to the nearest hundredth.
5.
Suppose that the population of a cer
tain town grows at an annual rate of 8%.
If the population is currently 4,000, how
many years will it take for it to double?
Round your answer to the nearest hun
dredth.
6.
Suppose that a certain radioactive
isotope has an annual decay rate of 19.2%.
Starting with a 443 gram sample, how
many grams will be left after 9 years?
Round your answer to the nearest hun
dredth.
7.
Suppose that a certain radioactive
isotope has an annual decay rate of 17.4%.
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1
What is the halflife (in years) of the iso
tope? Round your answer to the nearest
hundredth.
8.
Suppose that the population of a cer
tain town grows at an annual rate of 7%.
If the population is currently 8,000, how
many years will it take for it to reach
18,000? Round your answer to the near
est hundredth.
9.
Suppose that a certain radioactive
isotope has an annual decay rate of 17.3%.
Starting with a 214 gram sample, how
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 Radioactive Decay, HalfLife, Exponential decay, certain radioactive isotope, annual decay rate, 18,000

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