SOLUTION: in order to qualify for a race emily needs to go at an average speed of 100 mi/h for two laps. but she only goes 75mi/h on the first lap. How fast does she need to go on the second
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Question 341266: in order to qualify for a race emily needs to go at an average speed of 100 mi/h for two laps. but she only goes 75mi/h on the first lap. How fast does she need to go on the second lap to reach the average speed of 100 mi/h? Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! in order to qualify for a race emily needs to go at an average speed of 100 mi/h for two laps. but she only goes 75mi/h on the first lap.
Let distance of a lap = x miles
If rate = 75 mph, time = x/75 hrs
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How fast does she need to go on the second lap to reach the average speed of 100 mi/h?
Distance for 2 laps = 2x miles
If rate = 100 mph, time = (2x)/100 = x/50 hrs
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Time for her 2nd lap would have to be time for 2 laps - time for 1st lap
x/50-x/75 = (75x-50x)/(50*75) = 25x/(50*75) = x/150 hrs.
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distance/time = rate
x/(x/150) = 150 mph
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She would have to go 150 mph to average 100 mph for the 2 laps.
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Cheers,
Stan H.
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