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276 Chapter 3 Graphing Linear Equations in Two Variables 18. The graph shows the average height for boys based on age. Let x represent a boy’s age, and let y represent his height (in inches). a. Find a linear equation that represents the height of a boy versus his age. y 2.5x 31 b. Use the linear equation found in part (a) to predict the average height of a 5-year-old boy. 43.5 in. 50 40 30 Concept 3: Writing a Linear Model Given a Fixed Value and a Rate of Change 19. Andrés has a cell phone plan with a local telephone company. His bill is determined each month by a $39.99 flat fee plus $0.20 for each text message sent or received. (See Example 3.) a. Write a linear model to compute the monthly cost, y, of Andrés’s cell phone bill if x text messages are sent or received. b. Use the equation to compute Andrés’s cell phone bill for a month in which he sent or received a total of 40 text messages. $47.99 20. Anabel lives in New York and likes to keep in touch with her family in Texas. She uses 10-10-987 to call them. The cost of a long distance call is $0.53 plus $0.06 per minute. a. Write an equation that represents the cost, C, of a long distance call that is x minutes long. b. Use the equation to compute the cost of a long distance phone call that lasted 32 minutes. $2.45 21. The cost to rent a 10-ft by 10-ft storage space is $90 per month plus a nonrefundable deposit of $105. a. Write a linear equation to compute the cost, y, of renting a 10-ft by 10-ft space for x months. b. What is the cost of renting such a storage space for 1 year (12 months)? $1185.00 22. An air-conditioning and heating company has a fixed monthly cost of $5000. Furthermore, each service call costs the company $25. a. Write a linear equation to compute the total cost, y, for 1 month if x service calls are made. b. Use the equation to compute the cost for 1 month if 150 service calls are made. $8750.00 23. A bakery that specializes in bread rents a booth at a flea market. The daily cost to rent the booth is $100. Each loaf of bread costs the bakery $0.80 to produce. a. Write a linear equation to compute the total cost, y, for 1 day if x loaves of bread are produced. b. Use the equation to compute the cost for 1 day if 200 loaves of bread are produced. $260.00 24. A beverage company rents a booth at an art show to sell lemonade. The daily cost to rent a booth is $35. Each lemonade costs $0.50 to produce. a. Write a linear equation to compute the total cost, y, for 1 day if x lemonades are produced. b. Use the equation to compute the cost for 1 day if 350 lemonades are produced. $210.00 y 0.5x 35 y 0.8x 100 C 0.06x 0.53 y 0.20x 39.99 60 Average Height of Boys Based on Age 0 1 2 3 4 5 6 7 8 9 10 11 12 Height (in.) Age (yr) 20 10 0 y x (8, 51) (2, 36) (Source: National Parenting Council) Writing     Translating Expression     Geometry      Scientific Calculator     Video y 90x 105 y 25x 5000


miller_introductory_algebra_3e_ch1_3
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