SOLUTION: Liz drove the first half of a trip at 36 mi/h. At what speed should she cover the remaining half in order to average 45 mi/h for the whole trip

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Question 408764: Liz drove the first half of a trip at 36 mi/h. At what speed should she cover the remaining half in order to average 45 mi/h for the whole trip
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Liz drove the first half of a trip at 36 mi/h. At what speed should she cover the remaining half in order to average 45 mi/h for the whole trip
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1st half DATA:
distance = x miles ; rate = 36 mph ; time = x/36 hrs.
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Whole trip DATA:
distance = 2x miles ; rate = 45 mph ; time = 2x/45 hrs
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2nd half DATA:
distance = x miles;
time = (2x/45)-(x/36) = (72x-45x)/(45*36)
= 27x/(45*36) = x/(5*12) = x/60 hrs
rate = d/t = x/(x/60) = 60 mph
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Ans: 60 mph
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Cheers,
Stan H.
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