If I drive x mph for t hours and then y mph for 2t hours The

If I drive x mph for t hours and then y mph for 2t hours. Then what is expression for the average speed.

Solution

average speed = (total distance)/(total time)
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distance = rate*time
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Your Problem:
total distance = (xt)+ (2yt) = (x+2y)t miles
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total time = t + 2t = 3t hours
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Therefore, average speed = [(x+2y)t]/(3t) = (x+2y)/3 mph