where x represents the number of days engineers worked on straightening the Tower and y represents the number of millimeters (mm) the Tower was moved toward vertical. (In the end, the Tower will keep some of its famous lean.) (Reuters-9/7/2000) a) Make a table of values using x 0, 10, 20, and 60, and write the information as ordered pairs. b) Explain the meaning of each ordered pair in the context of the problem. c) Graph the equation using the information in a). Use an appropriate scale. d) Engineers straightened the Leaning Tower of Pisa a total of about 450 mm. How long did this take? 83) The relationship between altitude (in feet) and barometric pressure (in inches of mercury) can be modeled by y 0.001x + 29.86 for altitudes between sea level (0 feet) and 5000 feet, where x represents the altitude and y represents the barometric pressure. (From data taken from www.engineeringtoolbox.com) Altitude and pressure 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Altitude (in feet) 30.00 29.80 29.60 29.40 29.20 29.00 28.80 28.60 28.40 28.20 28.00 27.80 27.60 27.40 27.20 27.00 26.80 26.60 26.40 26.20 26.00 25.80 25.60 25.40 25.20 25.00 24.80 0 Barometric pressure (in in. of mercury) a) From the graph, estimate the pressure at the following altitudes: 0 ft (sea level), 1000 ft, 3500 ft, and 5000 ft. b) Determine the barometric pressures at the same altitudes in a) using the equation. Are the numbers close? 80) Kelvin is driving from Los Angeles to Chicago to go to college. His distance from L.A. is given by the equation y 62x where x represents the number of hours driven, and y represents his distance from Los Angeles. a) Complete the table of values and write the information as ordered pairs. x y 3 8 15 20 b) Label a coordinate system, choose an appropriate scale, and graph the equation. c) Explain the meaning of the ordered pair (20, 1240) in the context of the problem. d) What does the 62 in y 62x represent? e) How many hours of driving time will it take for Kelvin to get to Chicago if the distance between L.A. and Chicago is about 2034 miles? (Round to the nearest hour.) 81) The blood alcohol percentage of a 180 lb male can be modeled by y 0.02x where x represents the number of drinks consumed (1 drink 12 oz of beer, for example) and y represents the blood alcohol percentage. (Taken from data from the U.S. Dept. of Health and Human Services) a) Make a table of values using x 0, 1, 2, and 4, and write the information as ordered pairs. b) Explain the meaning of each ordered pair in the context of the problem. c) Graph the equation using the information in a). Use an appropriate scale. d) If a 180-lb male had a blood alcohol percentage of 0.12, how many drinks did he have? 82) Concern about the Leaning Tower of Pisa in Italy led engineers to begin reinforcing the structure in the 1990s. The number of millimeters the Tower was straightened can be described by y 1.5x www.mhhe.com/messersmith SECTION 4.1 Introduction to Linear Equations in Two Variables 153
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