350 CHAPTER 6 Algebra, Graphs, and Functions 99. Hanging Wallpaper Tanisha owns an interior design business. Her charge, C, for hanging wallpaper is $40 plus $0.30 per square foot of wallpaper she hangs, or C s 40 0.30 , = + where s is the number of square feet of wallpaper she hangs. a) Graph C s 40 0.30 , = + for s 500. ≤ * b) From the graph, estimate her charge if she hangs 300 square feet of wallpaper. $130 c) If her charge is $70, use the equation for C to determine how many square feet of wallpaper she hung. 100 square feet 100. Selling Chocolates Ryan sells chocolate on the Internet. His monthly profit, p, in dollars, can be estimated by p n 15 300, = − where n is the number of dozens of chocolates he sells in a month. a) Graph p n 15 300, = − for n 60. ≤ * b) From the graph, estimate his profit if he sells 40 dozen chocolates in a month. $300 c) How many dozens of chocolates must he sell in a month to break even? 20 dozens of chocolates 101. Security System The Kamdars installed a home security system that includes an installation fee of $75 plus a monthly service fee of $25. The total cost of the system is given by C x 75 25 , = + where x is the number of months of service. a) Graph C x 75 25 , = + for x 50. ≤ * b) From the graph, estimate the Kamdars’ total cost after 30 months. $825 c) If the Kamdars’ total cost is $975, estimate the number of months of service. 36 months 102. Earning Simple Interest When $1000 is invested in a savings account paying simple interest for a year, the interest, i, in dollars, earned can be determined by the formula i r 1000 , = where r is the interest rate in decimal form. a) Graph i r 1000 , = for r up to and including an interest rate of 15%. * b) If the interest rate is 4%, what is the simple interest? $40 c) If the interest rate is 6%, what is the simple interest? $60 103. Determining the Number of Defects The following graph shows the daily number of workers absent from the $ $ $ $ assembly line at J. B. Davis Corporation and the number of defects coming off the assembly line for each of 10 days. The line on the graph can be used to approximate the number of defects coming off the assembly line per day for a given number of workers absent. a) Determine the slope of the line using the two points indicated with ordered pairs. 2 b) Using the slope determined in part (a) and the y-intercept, (0, 9), determine the equation of the line. y x2 9 = + c) Using the equation you determined in part (b), determine the approximate number of defects for a day if 3 workers are absent. 15 defects d) Using the equation you determined in part (b), approximate the number of workers absent for a day if there are 17 defects that day. 4 workers 10 11 12 13 14 15 16 17 18 19 20 9 0 (5, 19) 2 3 4 5 (0, 9) Workers Absent Daily Number of Defects at J. B. Davis Corporation Number of Defects 1 104. Determining a Test Grade The following graph shows the hours studied and the test grades on a biology test for 8 students. The line on the graph can be used to approximate the test grade the student receives for the number of hours studied. Test Grade Test Grades on Biology Exam Hours Studied 1 2 3 4 5 (4, 96) (0, 53) 95 90 85 80 75 70 65 60 55 50 100 0 a) Determine the slope of the line using the two points indicated with ordered pairs. 10.75 *See Instructor Answer Appendix Sebra/Shutterstock
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