Chapter 2
Models of Growth: Rates of Change





WeBWorK2.6 Logarithms and Representation of Data

Exercises

The data in each of the following tables (Exercises 1-4) approximately fit either an exponential function or a power function. In each case, decide which, and find a formula that fits the data. Each formula should have one of the forms \(y=c b^t\), \(y=c e^{kt}\), or \(y=c t^k\), with explicit values for the constants. You may use the Plot Data tool to decide which formula to try, or you can do these exercises entirely with the numeric calculator. The Plot Data tool has the data for Exercise 1. You can edit the data entry for Exercises 2, 3, 4.

  1.
\(t\)
\(y\)
  2.
\(t\)
\(y\)
   
5
14.855
 
5
4.452
   
10
20.292
 
10
7.339
   
15
24.354
 
15
12.101
   
20
27.720
 
20
19.950
   
25
30.648
 
25
32.893

  3.
\(t\)
\(y\)
  4.
\(t\)
\(y\)
 
1
24.7
 
1
25.0
 
5
17.2
 
5
7.5
 
10
11.0
 
10
4.4
 
20
4.5
 
20
2.6
 
35
1.2
 
35
1.7
 
50
0.3
 
50
1.3
  1. The data in Table E1 are graphed in Figures E1, E2, and E3, in Cartesian, semilog, and log-log plots, not necessarily in that order.
    1. Decide whether the data come from a linear function, a power function, an exponential function, or none of these.

    2. Estimate \(f(2)\).

    3. Estimate \(f\,' (2)\).


  2. Table E1  Values
    of a function
    \(t\) \(f(t)\)
    0.27
    1.618
    0.80
    2.786
    1.33
    3.592
    1.86
    4.248
    2.39
    4.815
    2.92
    5.322
    3.45
    5.785
    3.98
    6.213
    4.51
    6.614
    5.04
    6.992
    5.57
    7.350

    Figure E1  A plot of data in Table E1

    Figure E2  A plot of data in Table E1

    Figure E3  A plot of data in Table E1

  3. The data in Table E2 are graphed in Figures E4, E5, and E6, in Cartesian, semilog, and log-log plots, not necessarily in that order.

    1. Decide whether the data come from a linear function, a power function, an exponential function, or none of these.
    2. Find a formula for \(f\) as a function of \(t\) .

  4. Table E2  Values
    of a function
    \(t\) \(f(t)\)
    0.27
    1.618
    0.80
    2.240
    1.33
    2.664
    1.86
    3.008
    2.39
    3.512
    2.92
    3.936
    3.45
    4.360
    3.98
    4.784
    4.51
    5.208
    5.04
    5.632
    5.57
    6.056

    Figure E4  A plot of data in Table E2

    Figure E5  A plot of data in Table E2

    Figure E6  A plot of data in Table E2

     

  5. Table E3   Population
    of Mexico
    Year Population
    (millions)
    1980
    67.38
    1981
    69.13
    1982
    70.93
    1983
    72.77
    1984
    74.66
    1985
    76.60
    1986
    78.59
    Table E3 shows the population of Mexico for each of the years 1980 through 1986.

    1. Find an exponential function that approximately fits these data.

    2. By what percentage did the population grow each year?

    3. What does your formula predict for the population in 2010? (The actual population in 2010 was about 111 million.)

     

     

  6. Table E4   Houston
    area population
    Year Population
    1850
    18,632
    1860
    35,441
    1870
    48,986
    1880
    71,316
    1890
    86,224
    1900
    134,600
    1910
    185,654
    1920
    272,475
    1930
    455,570
    1940
    646,869
    1950
    947,500
    1960
    1,430,394
    1970
    1,999,316
    1980
    2,905,344
    1990
    3,731,014
    2000
    4,671,230
    2010
    5,946,800
    Table E4 shows the U.S. Census data for the Houston, Texas, primary statistical metropolitan area over a period of 130 years.

    1. Show that the historic population data for Houston are approximated by an exponential function, and find a formula for the function.

    2. According to your model formula, how long does it take for Houston's population to double?

    3. If the growth pattern continues into the future, what will the Houston area population be in 2050?
    4.  

       

       

       

       

       

       

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