SOLUTION: wo trains are 2 kms apart. Speed of one train is 20m/s and the other train is running at 30 m/s .Lengths of the trains are 200 and 300m. In how much time do the trains cross eac

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: wo trains are 2 kms apart. Speed of one train is 20m/s and the other train is running at 30 m/s .Lengths of the trains are 200 and 300m. In how much time do the trains cross eac       Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 490243: wo trains are 2 kms apart. Speed of one train is 20m/s and the other train is running at 30 m/s .Lengths of the trains are 200 and 300m. In how much time do the trains cross eac Log On
Log in or register.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
I take it to mean "How long will it be until the trains
have crossed each other?"
I assume they are headed in the same direction
I want to know how long it takes for the head of the
train that is behind to reach the tail of the train
that is ahead.
I'll say the one ahead is the 20 m/sec train
If the slower train is behind, it will never catch up!
The distance the train behind has to go is:
+2000+-+200++=+1800+ m
The speed of the train behind is +30+ m/sec
From that you have to subtract the other train's
speed. +1800+=+%2830+-+20%29%2At+
+t+=+1800%2F10+
+t+=+180+ sec
Now how long does it take the tail of the train behind
to reach the head of the train ahead?
You can think of the train ahead as standing still and
the train behind traveling at the difference of their speeds
The train behind has to travel +300+%2B+200+=+500+ for it's
tail to reach the head of the other
+500+=+10%2At+
+t+=+50+ sec
The total time is +180+%2B+50+=+230+ sec
for the trains to pass each other.
Hope I got it.