Question 384391: a group of friends is planning a trip to miami, florida, they know that the distance beteween jackson and miami is 1385 miles and estimate that the trip should take them 20 1/4 hrs. they also know that the interstate speed limit in the states they will be driving through is either 65 or 60 mph. how many hours will they drive at each speed?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! a group of friends is planning a trip to miami, florida, they know that the distance between jackson and miami is 1385 miles and estimate that the trip should take them 20 1/4 hrs. they also know that the interstae speed limit in the states they will be driving through is either 65 or 60 mph. how many hours will they drive at each speed?
Let x be time driven at 65 mph; distance = 65x miles
Let y be time driven at 70 mph; distance = 70y miles
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Time Eq: x + y = 81/4 hrs
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Distance Eq: 65x + 70y = 1385
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Multiply thru the time Eq by 65 to get:
65x + 65y = 65*81/4
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Subtract that from the Distance Eq and solve for "x":
5y = 1385-65*81/4
5y = 68.75
y = 13.75 hrs (time driven at 70 mph)
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x = 20 1/4 - 13.75 = 6.5 hrs (time driven at 65 mph)
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Cheers,
Stan H.
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Stan H.
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