Presentation on theme: "D = r t 1) Two planes take off at the same time, departing in separate directions. One plane travels 3 times as fast as the other plane. After 3 hours,"— Presentation transcript:
d = r t 1) Two planes take off at the same time, departing in separate directions. One plane travels 3 times as fast as the other plane. After 3 hours, they are 1620 miles apart. What is the average speed of each plane? Make a table Plane 1 Plane 2 rate x time = distance r 3r 3 3 9r 3r + 9r = 1620 plane 1 d + plane 2 d = total d 12r = r = 135 Plane 1 = 135 mph Plane 2 = 3(135) = 405 mph 1620 miles P 1 = 3rP 2 = 9r
2) Rob and Joe live 4.5 miles apart. Joe leaves his house walking at 3 mph. However, at the same time Rob runs from his house at 6 mph. The are heading toward each other. How long will it be until they meet? Rob Joe rate x time = distance 6 3 t t 6t 3t 4.5 miles Joe = 3tRob = 6t Rob d + Joe d = total d 3t + 6t = 4.5 9t = t = 0.5 It will be ½ hour until they meet.
3) A train leaves the station averaging 40 mph. Four hours later a second train leaves a stations 440 miles away traveling toward the first train on an adjacent track at a rate of 60 mph. How long will it be until they pass each other? Train A Train B rate x time = distance t t – 4 40t 60(t-4) 440 miles A = 40t B = 60(t-4) A d + B d = total d 40t + 60(t – 4) = t + 60t – 240 = t – 240 = t = t = 6.8 hours Train A = 6 hrs. 48 min. Train B = 2 hrs. 48 min.
4) Sandis family left for vacation at the beach, driving an average of 55 mph. On the return trip they were only able to average 45 mph due to road construction. If the return trip took 2 hours longer, how far from the beach does Sandis family live? To Beach From Beach rate x time = distance t t t 45(t+2) To Beach = 55t From Beach = 45(t+2) Distances are the same! To d = From d 55t = 45(t + 2) 55t = 45t t 10t = t = 9 Distance = 55 9 = 495 miles