 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 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? plane 1 d + plane 2 d = total d Make a table 3r + 9r = 1620 12r = 1620 rate x time = distance 12 12 r Plane 1 3 3r r = 135 3r Plane 2 3 9r Plane 1 = 135 mph P 1 = 3r P 2 = 9r Plane 2 = 3(135) = 405 mph 1620 miles

It will be ½ hour until they meet. 4.5 miles
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? rate x time = distance Rob d + Joe d = total d 6 Rob t 6t 3t + 6t = 4.5 3 t 3t Joe 9t = 4.5 9 9 t = 0.5 Joe = 3t Rob = 6t It will be ½ hour until they meet. 4.5 miles

3) A train leaves the station averaging 40 mph
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? A d + B d = total d rate x time = distance 40t + 60(t – 4) = 440 40 Train A t 40t 40t + 60t – 240 = 440 60 t – 4 60(t-4) Train B 100t – 240 = 440 +240 +240 B = 60(t-4) A = 40t 100t = 680 100 100 440 miles t = 6.8 hours Train A = 6 hrs. 48 min. Train B = 2 hrs. 48 min.

4) Sandi’s 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 Sandi’s family live? To d = From d rate x time = distance 55t = 45(t + 2) 55 To Beach t 55t 55t = 45t + 90 -45t -45t 45 t + 2 45(t+2) From Beach 10t = 90 10 10 To Beach = 55t t = 9 From Beach = 45(t+2) Distance = 55  9 = 495 miles Distances are the same!

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