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:
1 d = r t1) 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 dMake a table3r + 9r = 162012r = 1620rate x time = distance1212rPlane 133rr = 1353rPlane 239rPlane 1 = 135 mphP 1 = 3rP 2 = 9rPlane 2 = 3(135)= 405 mph1620 miles
2 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 = distanceRob d + Joe d = total d6Robt6t3t + 6t = 4.53t3tJoe9t = 4.599t = 0.5Joe = 3tRob = 6tIt will be ½ hour until they meet.4.5 miles
3 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 drate x time = distance40t + 60(t – 4) = 44040Train At40t40t + 60t – 240 = 44060t – 460(t-4)Train B100t – 240 = 440+240+240B = 60(t-4)A = 40t100t = 680100100440 milest = 6.8 hoursTrain A = 6 hrs. 48 min.Train B = 2 hrs. 48 min.
4 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 drate x time = distance55t = 45(t + 2)55To Beacht55t55t = 45t + 90-45t-45t45t + 245(t+2)From Beach10t = 901010To Beach = 55tt = 9From Beach = 45(t+2)Distance = 55 9= 495 milesDistances are the same!