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Re: DS Relative Speed  Set 14 [#permalink]
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26 Sep 2010, 04:24
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Stations X and Y are connected by two separate, straight, parallel rail lines that are 250 miles long. Train P and train Q simultaneously left Station X and Station Y, respectively, and each train traveled to the other’s point of departure. The two trains passed each other after traveling for 2 hours. When the two trains passed, which train was nearer to its destination? (1) At the time when the two trains passed, train P had averaged a speed of 70 miles per hour. (2) Train Q averaged a speed of 55 miles per hour for the entire trip. (1) As P averaged 70 miles per hour at the time when the two trains passed, hence when they passed each other P traveled 2*70=140 miles, so for P it was 110 miles left to cover and for Q 140. P was closer to its destination. Sufficient. (2) Knowing average speed for entire trip won't help us to determine the distance either of train coverd at the time they passed each other (as the average speed at the time the met could have been different). Not sufficient. Answer: A.
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Re: DS Relative Speed  Set 14 [#permalink]
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17 Oct 2010, 05:48



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Re: Stations X and Y are connected by two separate, straight, [#permalink]
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31 Dec 2013, 08:05
tenaman10 wrote: Stations X and Y are connected by two separate, straight, parallel rail lines that are 250 miles long. Train P and train Q simultaneously left Station X and Station Y, respectively, and each train traveled to the other’s point of departure. The two trains passed each other after traveling for 2 hours. When the two trains passed, which train was nearer to its destination?
(1) At the time when the two trains passed, train P had averaged a speed of 70 miles per hour. (2) Train Q averaged a speed of 55 miles per hour for the entire trip. Clear A, from question stem, one gets the following (P+Q)(2) = 250 (P+Q) = 125 Statement 1 P= 70 > Q= 55 Suff Statement 2 Not suff Hence A is the correct answer Hope it helps! Cheers! J



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Re: Stations X and Y are connected by two separate, straight, [#permalink]
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11 Jan 2014, 07:38
Yes it is A. Stmt 2 is tricky. We should not assume speed of Q is constant. It got me.
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Re: Stations X and Y are connected by two separate, straight, [#permalink]
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01 May 2014, 06:48
What is the right answer ? To me both alone are sufficient.



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Re: Stations X and Y are connected by two separate, straight, [#permalink]
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01 May 2014, 07:05



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Re: Stations X and Y are connected by two separate, straight, [#permalink]
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05 May 2014, 23:28
HI bunnel Please explain once the concept of average speed... as in when we need the average speed of entire trip and when we need average speed at the time of meeting
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Re: Stations X and Y are connected by two separate, straight, [#permalink]
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06 May 2014, 03:21



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Re: Stations X and Y are connected by two separate, straight, [#permalink]
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20 Jan 2015, 10:32
Stations X and Y are connected by two separate, straight, parallel rail lines that are 250 miles long. Train P and train Q simultaneously left Station X and Station Y, respectively, and each train traveled to the other’s point of departure. The two trains passed each other after traveling for 2 hours. When the two trains passed, which train was nearer to its destination?
(1) At the time when the two trains passed, train P had averaged a speed of 70 miles per hour. (2) Train Q averaged a speed of 55 miles per hour for the entire trip
SOLUTION:
D = 250 miles P and Q travel 2 hrs each before they meet
From (1): P speed = 70 mph i.e. in 2 hrs it covers 140 miles Therefore, Q must have traveled = 110 miles  SUFFICIENT
From (2): Q speed for ENTIRE trip = 55 mph  Clearly INSUFFICIENT
ANSWER: A



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Re: Stations X and Y are connected by two separate, straight, [#permalink]
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09 Apr 2016, 14:52
i think it should be E.
1) it says "At the time the 2 trains passed" train P averaged 70 mph. Which means that the speed could've been more or less before. what if it was going at a speed of 30 mph and all along and then was at 70 around when it crossed train Q.
2) Train Q averaged 55 mph for the entire trip.
Here we're comparing apples to oranges as one states the speed when the trains crossed and one states the average speed. If both had average speeds in the question, it would be a fair comparison.



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Re: Stations X and Y are connected by two separate, straight, [#permalink]
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09 Apr 2016, 15:09



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Stations X and Y are connected by two separate, straight, [#permalink]
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01 Aug 2016, 03:56
Stations X and Y are connected by two separate, straight, parallel rail lines that are 250 miles long. Train P and train Q simultaneously left Station X and Station Y, respectively, and each train traveled to the other’s point of departure. The two trains passed each other after traveling for 2 hours. When the two trains passed, which train was nearer to its destination? (1) At the time when the two trains passed, train P had averaged a speed of 70 miles per hour. Train P has been running for 2 hours with an average speed of 70 miles per hour so it has covered 140 km . The total distance is 250; so P was 250140= 90 miles away from its destination . We can use logic to see that since the train are crossing each other then train Q must also travelled 90 kilometres and thus it was 25090 = 160 km away from its destination Train P was closer SUFFICIENT (2) Train Q averaged a speed of 55 miles per hour for the entire trip. Well the speed for first hour can vary from the second's hour's speed and so on. We don know at what speed train Q travelled for the first 2 hours so we cannot figure out its distance. INSUFFICIENT ANSWER IS A
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Stations X and Y are connected by two separate, straight, [#permalink]
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08 Dec 2016, 00:09
I don't know, but this one seems actually quite easy to me. Statement 1 says that at the time when the two trains passed, train P had average speed of 70 mph, that is after traveling 2 hours, which makes it 140. The rail lines are parallel and 250 long, meaning train P is 110 miles from its destination (250140), while train Q was 140 miles from its destination. Hence, statement 1 is sufficient. Hope it is clear.




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