A-16 ANSWERS 101. a) x C 400 200 600 800 1400 1200 1000 Cost ($) (20, 575) C 5 75 1 25x (0, 75) (50, 1325) 10 20 30 36 40 50 Number of Months 102. a) r i 40 20 60 80 100 120 140 160 Rate (%) i 5 1000r (15, 150) 2 4 6 8 10121416 Interest ($) 107. a) Solve the equations for y to put them in slope-intercept form. Then compare the slopes and y-intercepts. If the slopes are equal but the y-intercepts are different, then the lines are parallel. SECTION 6.7, PAGE 361 49. a) Cost for Ugly Truck Rentals: = + C x 0.79 30 Cost for Discount Rentals: = + C x 0.85 24 b) x 50 100 150 200 Cost ($) (100, 109) 50 100 150 200 Number of Miles C C 5 0.85x 1 24 C 5 0.79x 1 30 50. a) Tom’s Tree and Landscape: = + C h 60 200 Lawn Perfect: = + C h 25 305 b) h C Cost ($) (3, 380) 12345678910 Number of Hours of Labor 100 200 300 400 500 600 700 800 900 C 5 60h 1 200 Tom’s Tree and Landscape C 5 25h 1 305 Lawn Perfect 51. b) x 400 200 600 800 1000 1200 1400 Amount ($) (40, 1000) 10 20 30 40 50 Number of Backpacks R 5 25x Cost Revenue C R C 5 15x 1 400 52. b) x 5000 10,000 15,000 25,000 20,000 Amount ($) (110, 16,500) 25 50 75 100 125 150 Number of Units R C C 5 115x 1 3850 R 5 150x 53. b) x R C Amount ($) (162, 6480) 50 100 150 200 Number of Earbuds 5000 4000 3000 2000 1000 6000 7000 8000 C 5 15x 1 4050 R 5 40x 54. b) x R C Amount ($) (90, 11,250) 25 50 75 100 125 150 Number of Stands 5000 10000 15000 20000 C 5 50x 1 6750 R 5 125x 57. + = x y 15 + = x y 0.40 0.10 0.25(15) l l 7.5 of 40%, 7.5 of 10% 72. When solving a system of equations, if you obtain a true statement such as = 0 0, the system is dependent and has an infinite number of solutions. Therefore the student’s answer is not correct.
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