Objective - To solve word problems involving linear situations. Point and Slope Two Points A sky diver jumps from a plane at 11,000 ft. above the ground and descends at 15 ft./sec. A sky diver jumps from a plane. He is 10,100 ft. above the ground after 60 sec. and is 8300 ft. after 3 min. y = height (ft.) x = time (sec.) Start Value = b = 11,000 Change = m = -15

Change in price = $0.80/ brick y = 0.80x + b m = 0.80 A masonry company charges $0.80 a brick. The company will charge $465 for 500 bricks to be delivered to a site. If x = the number of bricks, and y = total cost, write an equation for y in terms of x. Slope y = mx + b Change in price = $0.80/ brick y = 0.80x + b m = 0.80 465 = 0.8(500) + b 465 = 400 + b Point -400 -400 500 bricks cost $465 65 = b (x, y) = (500, 465) y = 0.8x + 65

-3.95 -3.95 Suppose a 5 minute call costs $6.20 and a 20 minute call costs $18.05. Write an equation which describes cost y in terms of x minutes. (minutes, cost) (x, y) (5, 6.20) (20, 18.05) y = mx + b y2- y1 18.05 - 6.20 y = 0.79x + b m = = x2- x1 20 - 5 6.20 = 0.79(5) + b 11.85 m = = 0.79 6.20 = 3.95 + b 15 -3.95 -3.95 2.25 = b y = 0.79x + 2.25

Let p = # of pens purchased Let r = # of rulers purchased 3p + 1r = 12 Pens cost $3 each and rulers cost $1 each. If Jim spends $12, how many of each did he buy? Let p = # of pens purchased Let r = # of rulers purchased 3p + 1r = 12 12 10 8 6 4 2 -3p -3p 1r = -3p +12 # Rulers r = -3p +12 m = -3 b = 12 0 1 2 3 4 5 # Pens