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#1 2005-09-01 17:45:41

ganesh
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Registered: 2005-06-28
Posts: 20,922

Two trains

Two trains, 200 and 160 meters long take a minute to cross each other while traveling in the same direction and take only 10 seconds when they cross in opposite directions. What are the speeds at which the trains are traveling?

Time given to solve the problem = 60 seconds


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#2 2005-09-01 22:47:42

MathsIsFun
Administrator
Registered: 2005-01-21
Posts: 7,616

Re: Two trains

Let me see ... 10 seconds ... front of train A starts at rear of train B, then proceeds until the the end has passed the front of train B, so ... 30 seconds ...  it has covered 360 metres (relatively) in one minute,  ... 50 seconds ... and when going in the opposite ...ZZZTT...TIMES UP!!!

(My advice: don't type while answering)


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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#3 2005-09-02 17:54:47

John E. Franklin
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Registered: 2005-08-29
Posts: 3,588

Re: Two trains


igloo myrtilles fourmis

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#4 2005-09-02 18:14:43

ganesh
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Registered: 2005-06-28
Posts: 20,922

Re: Two trains

Total distance to be covered = 360 m
In the same direction, time taken = 60 seconds, speed = 6m/s
(This is t1-t2, where t1 is speed of the faster train and t2 is the speed of the slower train).
In opposite direction, time taken = 10 seconds, speed = 36m/s
(This is t1+t2)
Solving the two equations, t1=21 m/s and t2=15m/s smile


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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