Math Is Fun Forum

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 48,421

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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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

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)

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

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: Two trains

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igloo myrtilles fourmis

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 48,421

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

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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