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182 Chapter 2 Linear Equations in Two Variables and Functions 22. Loraine is enrolled in an algebra class that meets 5 days per week. Her instructor gives a test every Friday. Loraine has a study plan and keeps a portfolio with notes, homework, test corrections, and vocabulary. She also records the amount of time per day that she studies and does homework.The following data represent the amount of time she studied per day and her weekly test grades. a. Graph the points on a rectangular coordinate system. Do the data points appear to follow a linear trend? Time Studied per Day Weekly Test Grade (min) (percent) x y 60 69 70 74 80 79 90 84 100 89 b. Find a linear equation that relates Loraine’s weekly test score y to the amount of time she studied per day x. (Hint: Pick two ordered pairs from the observed data, and find an equation of the line through the points.) c. How many minutes should Loraine study per day in order to score at least 90% on her weekly examination? Would the equation used to determine the time Loraine needs to study to get 90% work for other students? Why or why not? d. If Loraine is only able to spend hr/day studying her math, predict her test score for that week. 12 23. 13, 42 10, 52 19, 22 Graphing Calculator Exercises 24. 14, 32 14, 12 12, 22 25. 10, 22 12, 122 11, 62 26. 12, 22 10, 32 14, 12 27. Use a Table feature to confirm your answers to Exercise 11(a). 28. Use a Table feature to confirm your answers to Exercise 12(a). 29. Graph the equation y175x 1087.5 on the viewing window 0 x 5 and 0 y 1200. Use the Value feature to support your answer to Exercise 19 by showing that the line passes through the points (2.5, 650) and (3.5, 475). 30. Graph the equation y400x 1420 on the viewing window 0 x 3 and 0 y 1600. Use the Value feature to support your answer to Exercise 20 by showing that the line passes through the points (1, 1020) and (1.5, 820). Test Score (%) Minutes 90 80 70 60 50 40 30 20 10 10 20 30 40 50 60 70 80 90 100 y x Expanding Your Skills Points are collinear if they lie on the same line. For Exercises 23–26, use the slope formula to determine if the points are collinear. (Hint: Three points are collinear if the slope calculated using one pair of points is equal to the slope calculated using a different pair of points.)


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