Reminder Round all answers to two decimal places unless otherwise indicated.
Dispersion Model Animal populations move about and disperse. A number of models for this dispersion have been proposed, and many of them involve the logarithm. For example, in
a. Make a graph of
b. How many pill bugs were to be found within
c. How far from the release point would you expect to find only a single individual?
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Functions and Change: A Modeling Approach to College Algebra (MindTap Course List)
- Reminder Round all answers to two decimal places unless otherwise indicated. Gray Wolves in Idaho The report cited in Example 4.6 tells us that in 2009, there were 870 gray wolves in Idaho, but that the population declined by 19 that year. For purposes of this problem, we assume that this 19 annual rate of decrease continues. a. Find an exponential model that gives the wolf population W as function of the time t in years since 2009. b. It is expected that the wolf population cannot recover if there are fewer than 20 individuals. How long must this rate of decline continue for the wolf population to reach 20?arrow_forwardReminder Round all answers to two decimal places unless otherwise indicated. The pH Scale Acidity of a solution is determined by the concentration H of hydrogen ions in the solution measured in moles per liter of solution. Chemists use the negative of the logarithm of the concentration of hydrogen ions to define the pH scale: pH=logH Lower pH values indicate a more acidic solution. a.Normal rain has a pH value of 5.6. Rain in the eastern United States often has a pH level of 3.8. How much more acidic is this than normal rain? b.If the pH of water in lake falls below a value of 5, fish often fail to reproduce. How much more acidic is this than normal water with a pH of 5.6?arrow_forwardReminder Round all answers to two decimal places unless otherwise indicated. Doubling Time If an investment earns an APR of r, as a decimal, compounded annually, then the time D, in years, required for the investment to double in value is given by D=log2log(1+r). a.Find the doubling time for an investment subject to an APR of 5 if interest is compounded annually. b.Plot the graph of the doubling time D versus the interest rate r, as a decimal. Use a horizontal span of 0 to 0.1. c.Does a small change in the interest rate have a greater effect on the doubling time if interest rates are low or if they are high?arrow_forward
- Reminder Round all answers to two decimal places unless otherwise indicated. Using the Laws of LogarithmsFor Exercises 1 through 6, suppose that lnA=3, lnB=4, and lnC=5. Evaluate the given expression. lnABCarrow_forwardReminder Round all answers to two decimal places unless otherwise indicated. Continuous CompoundingThis is a continuation of Exercise 22. In this exercise, we examine the relationship between APR and the APY when interest is compounded continuously-in other words, at every instant. We will see by means of an example that the relationship is Yearlygrowthfactor=eAPR,(4.1) and so APY=eAPR1(4.2) if both the APR and the APY are in decimal form and interest is compounded continuously. Assume that the APR is 10, or 0.1 as a decimal. a.The yearly growth factor for continuous compounding is just the limiting value of the function given by the formula in part b of Exercise 22. Find that limiting value to four decimal places. b.Compute eAPR with an APR of 0.1 as a decimal. c.Use your answers to parts a and b to verify that Equation 4.1 holds in the case where the APR is 10. Note: On the basis of part a, one conclusion is that there is a limit to the increase in the yearly growth factor and hence in the APY as the number of compounding periods increases. We might have expected the APY to increase without limit for more and more frequent compounding. 22. APR and APYRecall that financial institutions sometimes report the annual interest rate that they offer on investments as the APR, often called the nominal interest rate. To indicate how an investment will actually grow, they advertise the annual percentage yield, or APY. In mathematical terms, this is the yearly percentage growth rate for the exponential function that models the account balance. In this exercise and the next, we study the relationship between the APR and the APY. We assume that the APR is 10. or 0.1 as a decimal. To determine the APY when we know the APR, we need to know how often interest is compounded. For example, suppose for the moment that interest is compounded twice a year. Then to say that the APR is 10 means that in half a year, the balance grows by 102 or 5. In other words, the 12-year percentage growth rate is 0.12 as a decimal. Thus, the 12-year growth factor is 1+0.12. To find the yearly growth factor, we need to perform a unit conversion: One year is 2 half-year periods, so the yearly growth factor is (1+0.12)2 or 1.1025. a.What is the yearly growth factor if interest is compounded four times a year? b.Assume that interest is compounded n times each year. Explain why the formula for the yearly growth factor is (1+0.1n)n. c.What is the yearly growth factor if interest is compounded daily? Give your answer to four decimal places.arrow_forwardReminder Round all answers to two decimal places unless otherwise indicated. Gray Wolves in MichiganGray wolves recolonized in the Upper Peninsula of Michigan beginning in 1990. Their population has been documented as shown in the following table. 56 a.Explain why one expect an exponential model to be appropriate for these data. b.Find an exponential model for the data given. Year Wolves 1990 6 1991 17 1992 21 1993 30 1994 57 1995 80 1996 116 1997 112 1998 140 1999 174 2000 216 c.Graph the data and the exponential model. Would it be better to use a piecewise-defined function? d.Find an exponential model for 1990 through 1996 and another for 1997 through 2000. e.Write a formula for the number of wolves as a piecewise-defined function using the two exponential models. Is the combined model a better fit?arrow_forward
- Reminder Round all answers to two decimal places unless otherwise indicated. Note Some of the formulas below use the special number e, which was presented in the Prologue. A Population of Deer When a breeding group of animals is introduced into a restricted area such as a wildlife reserve, the population can be expected to grow rapidly at first, but to level out when the population grows to near the maximum that the environment can support. Such growth is known as logistic population growth, and ecologists sometimes use a formula to describe it. The number N of deer present at time 1 measured in years since the herd was introduced on a certain wildlife reserve has been determined by ecologists to be given by the function N=12.360.03+0.55t Figure1 a. How many deer were initially on the reserve? b. Calculate N(10) and explain the meaning of the number you have calculated. c. Express the number of deer present after 15 years using functional notation, and then calculate it. d. How much increase in the deer population do you expect from the 10th to the 15th year?arrow_forwardReminderRound all answers to two decimal places unless otherwise indicated. Inflation An economist tracks the price of a certain item at the beginning of several years and compiles the following table. Years Price, in dollars 2013 265.50 2014 273.47 2015 281.67 2016 290.12 a. Show that the price is growing as an exponential function. b. Find an exponential model for the data. c. At the beginning of some year, the price will surpass 325. Use your model to determine which year.arrow_forwardReminder Round all answers to two decimal places unless otherwise indicated. Logistic Model A population grows according to the logistic model. The r value is 0.02 and the environmental carrying capacity is 2500. Write the logistic equation satisfied by the population if N(0)=100.arrow_forward
- Reminder Round all answers to two decimal places unless otherwise indicated. Energy Requirements for India In 2009, India consumed 20 exajoules of energy from all sources. one exajoule is 1018joules. It is anticipated that energy requirements for India will increase by 8 per year for the foreseeable future. a.Make an exponential model for India that shows energy requirements E, in exajoules, t years after 2009. b.What are the expected energy requirements for India in 2030?arrow_forwardReminder Round all answers to two decimal places unless otherwise indicated. Growth of Bacteria The organism E. coli is a common bacterium. Under certain conditions, it undergoes cell division approximately each 20minutes. During cell division, each cell divides into two cells. a.Explain why the number of E. coli cells present is an exponential function of time. b.What is the hourly growth factor for E. coli? c.Express the population N of E. coli as an exponential function of time t measured in hours. Use N0 to denote the initial population. d.How long will it take a population of E. coli to triple in size?arrow_forwardReminder Round all answers to two decimal places unless otherwise indicated. Radioactive Iodine Iodine-131 is a radioactive form of iodine. After the crisis at a Japanese nuclear power plant in March 2011, elevated levels of this substance were detected thousands of miles away from Japan. Iodine-131 has a half-life of 8days. What is the daily decay factor for this substance?arrow_forward
- Functions and Change: A Modeling Approach to Coll...AlgebraISBN:9781337111348Author:Bruce Crauder, Benny Evans, Alan NoellPublisher:Cengage Learning