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trains

by ketkoag » Tue Jul 21, 2009 3:51 am
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.

please lemme know what should be the answer.. IMO : D
I don't have OA though..
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I go for D

by struggling_guy2001 » Tue Jul 21, 2009 3:56 am
D is the correct option in my opinion.
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by shibal » Tue Jul 21, 2009 3:58 am
IMO A,
In stmt 1 we know that they meet when P travels at 70mph... We can then see rt=d for both trains
In stmt 2 I know that train Q's speed is of 55 mph for the whole trip, but i don't know nothing about the time he met P or the rate of P... So insuff..

Let's see what the others say
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by shibal » Tue Jul 21, 2009 3:58 am
IMO A,
In stmt 1 we know that they meet when P travels at 70mph... We can then see rt=d for both trains
In stmt 2 I know that train Q's speed is of 55 mph for the whole trip, but i don't know nothing about the time he met P or the rate of P... So insuff..

Let's see what the others say
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by raghavsarathy » Tue Jul 21, 2009 7:04 am
IMO - A

From Statement 1
We know that when the trains cross each other, Train P has travelled 70*2 = 140 miles and train Q the remain distance of 90 miles. Hence train P travelled a longer distance and is closer to its destination

From Statement 2
We need the avg speed till the point they meet.. Avg speed for the entire journey is over here is misleading. It is possible that train Q travels at 30 mph till they cross and then suddenly increases its speed to 100 miles per hour. In this case it is farther from its destination even though its avg speed may be higher that P's
Hence B is not sufficient
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by ketkoag » Wed Jul 22, 2009 1:09 am
ohh, i think answer should be B.
previously i thought it could be D but when i attempted it again i came across very minute details..
statement 1 says that train A was going 70mph "at the time the two trains passed" but what about before and after the trains passed. We need a constant average speed to tell the distance traveled. insuff

B says that the train Q averaged 55 miles/h for the entire trip.. so we do have the constant speed. and hence we can calculate the shorter distance..

So IMO B..
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by tohellandback » Wed Jul 22, 2009 2:19 am
IMO A

1)it HAD averaged i.e it already covered 2*70=140 miles. SUFFICIENT

2) INSUFF- the average speed given is for entire trip. Just imagine the train might have traveled at the speed of light before passing the other train and turned into a snail after that.
or the opposite of it.
The powers of two are bloody impolite!!
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by mmslf75 » Sun Dec 27, 2009 12:58 am
ketkoag 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.

please lemme know what should be the answer.. IMO : D
I don't have OA though..
...

I M O ::: A

St 1 Gives that at 2nd hr, P completed 140, and 110 more to go.
At that time Q has covered 110 and 140 more to go
Moment when the 2nd hour struck ;-)
St 2 Remember, when AVG Speed is stated, its NOT CONSTANT speed
We can caliculate total time Q takes 4.54 hrs (precisely)
What happens at 2nd hr no1 knows

A wins
Last edited by mmslf75 on Mon Dec 28, 2009 8:59 am, edited 1 time in total.
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by linkinpark » Mon Dec 28, 2009 8:58 am
I'm going to pick B

from 1 we don't know what was avg speed of first train or before passing speed or after passing speed so insufficient

from stmt 2 we know 55 is avg speed and both travelled for 2 hours till the time of passing so train B must have travelled 110 km, which mean train A must have travelled 140 km out of 250 km, hence Train A is near to destination after passing.
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by mmslf75 » Mon Dec 28, 2009 9:00 am
linkinpark wrote:I'm going to pick B

from 1 we don't know what was avg speed of first train or before passing speed or after passing speed so insufficient

from stmt 2 we know 55 is avg speed and both travelled for 2 hours till the time of passing so train B must have travelled 110 km, which mean train A must have travelled 140 km out of 250 km, hence Train A is near to destination after passing.
linkinpark,

see my explanation above, I have edited my post..!! :-)
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by linkinpark » Mon Dec 28, 2009 9:14 am
mmslf75 wrote:
linkinpark wrote:I'm going to pick B

from 1 we don't know what was avg speed of first train or before passing speed or after passing speed so insufficient

from stmt 2 we know 55 is avg speed and both travelled for 2 hours till the time of passing so train B must have travelled 110 km, which mean train A must have travelled 140 km out of 250 km, hence Train A is near to destination after passing.
linkinpark,

see my explanation above, I have edited my post..!! :-)
I thought of A as well and now you made me slightly confuse :D tried to google the question and got more confused, hence I'm abandoning this question until some expert comments.

https://www.urch.com/forums/gmat-data-su ... t-1-a.html original poster says answer is B but I'm now confused.
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by papgust » Mon Dec 28, 2009 6:00 pm
I guess it should be A.

As others are right about B, Q has an average speed of 55 for the entire trip. It is possible for Q to have travelled at more than 55 before meeting A and to have travelled at 30 or 40 after they meet. Or it could be the vice versa. Hence, insufficient.
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by yserious » Tue Dec 29, 2009 6:35 am
papgust wrote:I guess it should be A.

As others are right about B, Q has an average speed of 55 for the entire trip. It is possible for Q to have travelled at more than 55 before meeting A and to have travelled at 30 or 40 after they meet. Or it could be the vice versa. Hence, insufficient.
sorry for sounding completely stupid out here..
hw abut E?
In A and B, The train Q has an average of 55 and train P averaged 70 when it crossed train Q..but nowhere we know tat the trains traveled at a uniform speed..bth for train P and Q

isnt it possible...train Q had an average of say 75 miles/hour before crossing and then it slowed the speed?
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