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Two trains 1& 2 start simultaneously and run on parallel

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Joined: 13 May 2013
Posts: 20
Two trains 1& 2 start simultaneously and run on parallel [#permalink]

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23 Nov 2013, 03:57
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67% (01:34) correct 33% (01:36) wrong based on 220 sessions

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Two trains 1& 2 start simultaneously and run on parallel tracks between stations A and B .They pass each other after after "t" hours from the start.How much time does the train 2 takes to cover the remaining distance after they pass each other?

1) speed of train 1 is 4 times the speed of train 2.

2) after passing each other train 1 takes 4 hours to complete the remaining distance between the stations.
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Joined: 10 Oct 2012
Posts: 625
Re: Two trains 1& 2 start simultaneously and run on parallel [#permalink]

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24 Nov 2013, 00:27
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innocous wrote:
Two trains 1& 2 start simultaneously and run on parallel tracks between stations A and B .They pass each other after after "t" hours from the start.How much time does the train 2 takes to cover the remaining distance after they pass each other?

1) speed of train 1 is 4 times the speed of train 2.

2) after passing each other train 1 takes 4 hours to complete the remaining distance between the stations.

Let the speed of train 1 be$$v_1$$ and that of train 2 be $$v_2$$; the distance between A and B : 5d

From F.S 1, $$v_1 = 4*v_2.$$.Thus,we know that the distance covered by train 1 and train 2 when they meet are in the ratio of 4:1. Hence, the distance covered by train 1 is 4d and that by train 2 is d. Thus time taken by train 2 to cover the remaining distance : $$\frac{4d}{v_2}$$ Clearly Insufficient.

F.S 2 states that train 1 takes 4 hours to cover the remaining distance. We have no relation between the two speeds,hence clearly Insufficient.

Taking both together, we know that $$\frac{d}{v_1} = 4 hours \to \frac{d}{4v_2} = 4.$$

Thus, $$\frac{4d}{v_2}$$ $$= 4*16 = 64 hours.$$

Sufficient.

C.
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Joined: 07 Sep 2014
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Re: Two trains 1& 2 start simultaneously and run on parallel [#permalink]

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30 Aug 2016, 00:59
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Two trains 1& 2 start simultaneously and run on parallel tracks between stations A and B .They pass each other after after "t" hours from the start.How much time does the train 2 takes to cover the remaining distance after they pass each other?

1) speed of train 1 is 4 times the speed of train 2.

2) after passing each other train 1 takes 4 hours to complete the remaining distance between the stations.

what train 2 has taken to cover, train 1 will take 1/4 th of it so in 1 hr they will meet.
so before meeting at the somewhere in between A & B, train 2 took 1 hr. that 1 hr will be 15 minute for train 1.
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Re: Two trains 1& 2 start simultaneously and run on parallel [#permalink]

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15 Jan 2018, 07:35
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: Two trains 1& 2 start simultaneously and run on parallel   [#permalink] 15 Jan 2018, 07:35
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