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Unformatted text preview: Home > My Assignments > Section 7.4 (Homework) About this Assignment SMALL BRIAN DIXON MA 241, section 009, Fall 2005 Instructor: Drew Pasteur North Carolina State University Due: Wednesday, October 19, 2005 11:03 PM EDT Description Exponential Growth Current Score: 0 out of 16.5 and Decay Question Score 1. [SCalcCC2 7.4.02.] A common inhabitant of human intestines is the bacterium Escherichia coli. A cell of this bacterium in a nutrient-broth medium divides into two cells every 20 minutes. The initial population of a culture is 60 cells. (a) Find the relative growth rate. k = (No Response)[2.08] (b) Find an expression for the number of cells after t hours. P(t) = (No Response) [60*exp(ln(8)*t)] (c) Find the number of cells after 8 hours. (No Response)[1.00663296] billion cells (d) Find the rate of growth after 8 hours. (No Response)[2.09323439424814] billion cells per hour (e) When will the population reach 20000 cells? (No Response)[2.79] h pts subs 1 -/1 -/20 2 -/1 -/20 3 -/1 -/20 4 -/1 -/20 5 -/1 -/20 Notes pts subs 1 -/1 -/20 2 -/1 -/20 3 -/1 -/20 4 -/1 -/20 5 -/1 -/20 -/0. 6 -/20 5 Notes 2. [SCalcCC2 7.4.06.] The table gives the population of the United States, in millions, for the years 1900 - 2000. (a) Use the exponential model and the census figures for 1900 and 1910 to predict the population in 2000. (No Response)[514] million What was the actual population in 2000? (No Response)[275] million (b) Use the exponential model and the census figures for 1980 and 1990 to predict the population in 2000. (No Response)[275] million Use this model to predict the population in the year 2010. (No Response)[303] million Use this model to predict the population in the year 2020. (No Response)[334] million (c) Draw a graph showing both of the exponential functions in parts (a) and (b) together with a plot of the actual population. (Do this on paper. Your teacher may ask you to turn in this work.) Are these models reasonable ones? (_) (_) Model (a) and Model (b) are both accurate (_) (_) Model (a) is accurate and Model (b) is not (_) (o) Model (a) is not accurate but Model (b) is accurate (_) (_) Neither Model (a) nor Model (b) are accurate 3. [SCalcCC2 7.4.08.] Bismuth-210 has a half-life of 5.0 days. pts subs 1 -/1 -/20 2 -/1 -/20 3 -/1 -/20 Notes (a) A sample originally has a mass of 800 mg. Find a formula for the mass remaining after t days. y(t) = (No Response) [800*exp((ln(2)*t)/(-5))] (b) Find the mass remaining after 10 days. (No Response)[200] mg (c) When is the mass reduced to 1 mg? (No Response)[48.2] days (d) Sketch the graph of the mass function. (Do this on paper. Your teacher may ask you to turn in this work.) pts subs 1 -/3 -/20 Notes 4. [SCalcCC2 7.4.12.] A curve passes through the point (0,4) and has the property that the slope of the curve at every point P is twice the ycoordinate of P. What is the equation of the curve? y(x) = (No Response) [4*exp(2*x)] Home My Assignments ...
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## This note was uploaded on 10/21/2009 for the course MATH MA241 taught by Professor Hubbard during the Spring '09 term at N.C. Central.

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