Question 199154: A train 1000 m long travels through a 3000 m tunnel. If 30 seconds elapse from the time the last car enters the tunnel until the time when the engine emerges from the other end, the speed of the train, in meters per second, is:
a 100/3 b 200/3 c 100 d 1000 e None of these
Found 2 solutions by rfer, Edwin McCravy:
Answer by rfer(16322)   (Show Source):
Answer by Edwin McCravy(20056)  (Show Source):
You can put this solution on YOUR website! Edwin's solution:
A train 1000 m long travels through a 3000 m tunnel. If 30 seconds elapse from the time the last car enters the tunnel until the time when the engine emerges from the other end, the speed of the train, in meters per second, is:
a 100/3 b 200/3 c 100 d 1000 e None of these
Let this line be the track inside the tunnel with the
1000, 2000, and 3000 meter markers:
Put the train just inside the tunnel, with the engine
at the 1000 meter marker, and the last car at the 0
meter marker, the left end of the tunnel.
Now when the engine is at the 3000 meter marker which
is the right end of the tunnel, we have this:
So the engine only traveled 2000 meters, from
the 1000 meter marker to the 3000 meter marker,
So the engine has traveled 2000 meters.
Since 
 
Edwin
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