Chap8 Section7

# Elementary and Intermediate Algebra: Graphs & Models (3rd Edition)

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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%. Copyrighted material. See: 1 What is the half-life (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 many grams will be left after 5 years? Round your answer to the nearest hun- dredth. 10. Suppose that the population of a certain town grows at an annual rate of 7%. If the population grows to 2 , 000 in 7 years, what was the original popula- tion? Round your answer to the nearest integer. 11. Suppose that the population of a certain town grows at an annual rate of 3%. If the population is currently 3,000, how many years will it take for it to dou- ble? Round your answer to the nearest hundredth.

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