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Stations X and Y are connected by two separate, straight,

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Stations X and Y are connected by two separate, straight,  [#permalink]

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New post Updated on: 27 Jun 2013, 00:34
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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.

Originally posted by udaymathapati on 30 Aug 2010, 10:23.
Last edited by Bunuel on 27 Jun 2013, 00:34, edited 1 time in total.
Edited the OA.
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Re: Two Trains  [#permalink]

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New post 30 Aug 2010, 10:58
udaymathapati 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.


Straight A, the asnwer cannot be C.

(1) As P averaged 70 miles per hour at the time when the two trains passed, hence whey 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' help us to determine the distance either of train covered 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: Two Trains  [#permalink]

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New post 30 Aug 2010, 21:15
Agree with Bunuel. Pretty, pretty, pretty good.
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Re: Two Trains  [#permalink]

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New post 31 Aug 2010, 03:44
Yes.. agree.... Atually i was shocked to see C in the answer....
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Re: Two Trains  [#permalink]

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New post 31 Aug 2010, 10:15
I agree with bunuel here....Has to be A
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Stations X and Y are connected by two seperate.....  [#permalink]

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New post 08 Jan 2016, 15:36
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.


I have found the answer to this question, BUT I have not found the answer to my question. For some reason, the answer is not making sense in my mind. Can someone explain how A is the correct answer, and C is incorrect? For statement 1, how do we know that Train Q had not averaged a speed of 80mph?

Thank you in advance!
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Re: Stations X and Y are connected by two separate, straight,  [#permalink]

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New post 08 Jan 2016, 16:03
1
Jscheu91 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.


I have found the answer to this question, BUT I have not found the answer to my question. For some reason, the answer is not making sense in my mind. Can someone explain how A is the correct answer, and C is incorrect? For statement 1, how do we know that Train Q had not averaged a speed of 80mph?

Thank you in advance!


Make sure to follow all posting guidelines (link in my signatures) especially to search for a question before you post an already discussed question as a new one.

Merged the topics. Refer above for the solution.

Statement 1 should have given you an indication that average speed of the entire trip might be different from the average speed at the very moment that the trains passed each other.

This statement lets you setup the following information : 2P+2Q=250 , with P=70, giving you Q = 55 at that very moment. WIth this information, you can definitely calculate unique values of distances for both the trains.

Statement 2, tells you about the average speed of Q for the ENTIRE TRIP. This doesn't help in any way. Thus not sufficient.

A is thus the correct answer.

Hope this helps.
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Re: Stations X and Y are connected by two separate, straight,  [#permalink]

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New post 23 Jul 2017, 03:14
Sorry but the explanation for statement 1 is not clear from the above thread. Can someone please explain how do we know the speed of Q and how do we derive that equation. Thank you.
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Re: Stations X and Y are connected by two separate, straight,  [#permalink]

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New post 23 Jul 2017, 05:38
longhaul123 wrote:
Sorry but the explanation for statement 1 is not clear from the above thread. Can someone please explain how do we know the speed of Q and how do we derive that equation. Thank you.



X------(140 miles)--------(meeting point)------(110 miles)-----Y
P -->..........................................................................<--Q

Trains meet after 2 hours. Train P's rate was 70 miles per hour at the time when the two trains met, hence P traveled 2*70=140 miles. Thus Q traveled 250 - 140 = 110 miles. We don't need the rate of Q to answer the question but we can get it. It would be (distance traveled)/(time) = 110/2 = 55 miles per hour.
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Re: Stations X and Y are connected by two separate, straight,  [#permalink]

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New post 17 Jan 2018, 11:37
Bunuel wrote:
udaymathapati 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.


Straight A, the asnwer cannot be C.

(1) As P averaged 70 miles per hour at the time when the two trains passed, hence whey 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' help us to determine the distance either of train covered at the time they passed each other (as the average speed at the time the met could have been different). Not sufficient.

Answer: A.


Bunuel
I did not understand still that even if option 1 gives us P is 110 miles away from destination how can we conclude that P is nearer at that time without knowing anything about Q?
If we are to compare P & Q's distance from the destination when they pass each other, we need to know Q's distance too at that time right?
Please help me understand this.
Thanks!
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Re: Stations X and Y are connected by two separate, straight,  [#permalink]

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New post 17 Jan 2018, 12:25
1
Shenaz wrote:
Bunuel wrote:
udaymathapati 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.


Straight A, the asnwer cannot be C.

(1) As P averaged 70 miles per hour at the time when the two trains passed, hence whey 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' help us to determine the distance either of train covered at the time they passed each other (as the average speed at the time the met could have been different). Not sufficient.

Answer: A.


Bunuel
I did not understand still that even if option 1 gives us P is 110 miles away from destination how can we conclude that P is nearer at that time without knowing anything about Q?
If we are to compare P & Q's distance from the destination when they pass each other, we need to know Q's distance too at that time right?
Please help me understand this.
Thanks!


P is 110 miles from the destination at the moment when P and Q meet. Since the whole distance is 250 miles, then Q is 250 - 110 = 140 miles from the destination.
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New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


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

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New post 22 Jan 2018, 05:22
thanks for the explanation, i missed that were traveling from opp ends

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Re: Stations X and Y are connected by two separate, straight, &nbs [#permalink] 22 Jan 2018, 05:22
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