SOLUTION: The distance from Spokane to Pasco by train is 150 miles. The train ride is direct with no stops along the way except that the train stops every 30 miles to let freight trains pass

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Question 1025323: The distance from Spokane to Pasco by train is 150 miles. The train ride is direct with no stops along the way except that the train stops every 30 miles to let freight trains pass. The trip takes 2 hours and 40 minutes. Suppose its average speed is 100 mph. What is the average wait time for letting freight trains pass? Express your answer to the nearest second.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The train's average speed does not
include time when it is stopped
+150+%2F+30+=+5+
It stops 5 times to let freight trains pass
Let +t+ = time in hrs for each of the stops
+5t+ = total time spent stopped
+2.667+-+5t+ = total travel time
( 40 mins = .667 hrs )
----------------
+150+=+100%2A%28+2.667+-+5t+%29+
+150+=+266.667+-+500t+
+500t+=+116.667+
+t+=+.23333+ hrs
+.23333%2A60+=+14+ min
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The average wait time is 14 min
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check:
+150+=+100%2A%28+2.667+-+5t+%29+
+150+=+100%2A%28+2.6667+-+5%2A.2333+%29+
+1.5+=+2.6667+-+1.16667+
+1.5+=+1.5+
OK