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A jet goes from City 1 to City 2 at an average speed of 600 miles per hour, and returns along the same path at an average speed if 300 miles per hour. What is the average speed, in miles per hour, for the trip

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Answer:

400 m/hr average

Step-by-step explanation:

d = distance = rate * time

d/r  = time

for going   d /600 = t  Going

for returning  d/300 = t  returning

total distance is  d+d = 2d

total time =   d/600 + d/300

Average speed = distance / time = 2d / ( d/600+ d/300)

                                                       = 2d / [(d+2d)/600]

                                                       = 2d / (3d/600) =  600*2/3 = 400 avg

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