Download Attendance Quiz 11

TU
Math 55
SS-II 2004
Yun Yoo
Attendance Quiz 11
Name:
Date : Monday, July 26
1. (Doubling Time) Give a doubling time for an exponentially growing quantity.
(a). The doubling time of a population of flies is 3 hours. By what factor does the
population increase in 24 hours? In 1 week?
(b). The doubling time of a city’s population is 22 years. How long does it take for the
population to quadruple?
(c). The initial population of a town is 15,600, and it grows with a doubling time of 20
years. What will the population be in 12 years? In 24 years?
TU
Math 55
SS-II 2004
Yun Yoo
(d). The number of cells in a tumor doubles every 1.5 months. If the tumor begins as a
single cell, how many cells will there be after 3 years? After 6 years?
2. (World Population.)In 2000, world population was 6 billion. Use the given doubling
time to predict the population in 2010, 2060, and 2100. Assume a doubling time of 45
years.
3. (Doubling Time Formula.) Use the approximate doubling time formula (rule of 70). Be
sure to discuss whether the formula is valid for the case described.
Prices are rising at a rate of 0.7 % per month. What is their doubling time? By what factor
will prices increase in 1 year? In 8 years?
TU
Math 55
SS-II 2004
Yun Yoo
4. (Half -Life.) Give a half-life for an exponentially decaying quantity.
(a). The half-life of a radioactive substance is 35 years. If you start with some amount of
this substance, what fraction will remain in 70 years? In 140 years?
(b). The half-life of a drug in the bloodstream is 12 hours. By what factor does the
concentration of the drug decrease in 24 hours? In 36 hours?
(c). The current population of a threatened animal species is 1 million, but is declining
with a half-life of 10 years. How many animals will be left in 40 years? In 70 years?