Question 823625: If Rachel travels 2 miles on local roads and 12 miles on the highway. Her speed on the highway was twice her speed on local roads. Her driving time was 16 minutes. Whats her speed for each part of the trip?
Please show work and explain!
Answer by TimothyLamb(4379)   (Show Source):
You can put this solution on YOUR website! ---
s = d / t
s = speed
d = distance
t = time
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t = d / s
is the same equation, just solved for time
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Rachel's trip was composed of two segments, the local road segment (A), and the highway segment (B).
We're told that both segment together took 16 minutes to complete.
16 minutes * (1/60 hours/minutes) = 16/60 hours
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Adding the time it took her to drive segment A to the time it took her to drive segment B, the sum = 16/60 hours
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Time for segment A = 2/s
s is Rachel's speed during segment A
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Time for segment B = 12/2s
2s is Rachel's speed during segment B (we're told that segment B speed is twice segment A speed)
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t = d / s
t = 16/60 hours
t = 2/s + 12/2s
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2/s + 12/2s = 16/60
4/2s + 12/2s = 16/60
16/2s = 16/60
2s = 16/(16/60)
2s = 60
s = 30 mph
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answer:
speed on local roads = 30 mph
speed on the highway = 60 mph
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