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goyalsau: Legendary Member; Posts: 866; Joined: Mon Aug 02, 2010 6:46 pm; Location: Gwalior, India; Thanked: 31 times

by goyalsau » Tue Dec 07, 2010 3:27 am

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Source: Beat The GMAT — Data Sufficiency | Tue Dec 07, 2010 3:27 am

abhishekg21: Senior | Next Rank: 100 Posts; Posts: 49; Joined: Tue May 11, 2010 5:46 am; Thanked: 3 times

by abhishekg21 » Tue Dec 07, 2010 3:51 am

i think it should be A.
if speed is same then they will always meet at mid point.
since A tells us about total distance it is sufficient.
B is not as we dont know how much speed was reduced.

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goyalsau: Legendary Member; Posts: 866; Joined: Mon Aug 02, 2010 6:46 pm; Location: Gwalior, India; Thanked: 31 times

by goyalsau » Tue Dec 07, 2010 4:04 am

abhishekg21 wrote:i think it should be A.
if speed is same then they will always meet at mid point.
since A tells us about total distance it is sufficient.
B is not as we dont know how much speed was reduced.

Even I marked A, But the OA is C

Saurabh Goyal
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EveryBody Wants to Win But Nobody wants to prepare for Win.

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beat_gmat_09: Master | Next Rank: 500 Posts; Posts: 437; Joined: Sat Nov 22, 2008 5:06 amFollowed by: 1 member; Location: India; Thanked: 50 times; GMAT Score:580

by beat_gmat_09 » Tue Dec 07, 2010 4:39 am

A & B together.
Sum of both the trains is given to be same.
A) Distance P-Q is 200km, after reducing the speed, distance is still 200km.
B) Sum of speeds is 50km/hr, time taken to meet will be same and is given by Relative speed = Distance / time
from A & B rel speed = 50, distance = 200km.
50 = 200/t, t = 4hours.
In 4 hours train from P will travel = s*t = 25*4 = 100km
They meet at the center, as is obvious, their speeds are same before and even after reducing by equal amounts.

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goyalsau: Legendary Member; Posts: 866; Joined: Mon Aug 02, 2010 6:46 pm; Location: Gwalior, India; Thanked: 31 times

by goyalsau » Tue Dec 07, 2010 4:53 am

beat_gmat_09 wrote:A & B together.
Sum of both the trains is given to be same.
A) Distance P-Q is 200km, after reducing the speed, distance is still 200km.
B) Sum of speeds is 50km/hr, time taken to meet will be same and is given by Relative speed = Distance / time
from A & B rel speed = 50, distance = 200km.
50 = 200/t, t = 4hours.
In 4 hours train from P will travel = s*t = 25*4 = 100km
They meet at the center, as is obvious, their speeds are same before and even after reducing by equal amounts.

Two trains 'A' and 'B' starting from points P and Q respectively travel with the same speed towards each other and meet after a certain time. If the speed of each train is reduced by the same amount, then they take two more hours to meet. At what distance from P do the trains meet?

HI! Beat_gmat_09, You solved it with equation and get the result in the end that they will meet at the center point.

We know that the speed of both the trains are Same, So irrespective of the speed they will meet center, Take any two object's if the speed is same they will always meet at the center, It does not matter what time they take to travel the distance.

Saurabh Goyal
[email protected]
-------------------------

EveryBody Wants to Win But Nobody wants to prepare for Win.

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beat_gmat_09: Master | Next Rank: 500 Posts; Posts: 437; Joined: Sat Nov 22, 2008 5:06 amFollowed by: 1 member; Location: India; Thanked: 50 times; GMAT Score:580

by beat_gmat_09 » Tue Dec 07, 2010 4:57 am

goyalsau wrote:
beat_gmat_09 wrote:A & B together.
Sum of both the trains is given to be same.
A) Distance P-Q is 200km, after reducing the speed, distance is still 200km.
B) Sum of speeds is 50km/hr, time taken to meet will be same and is given by Relative speed = Distance / time
from A & B rel speed = 50, distance = 200km.
50 = 200/t, t = 4hours.
In 4 hours train from P will travel = s*t = 25*4 = 100km
They meet at the center, as is obvious, their speeds are same before and even after reducing by equal amounts.
Two trains 'A' and 'B' starting from points P and Q respectively travel with the same speed towards each other and meet after a certain time. If the speed of each train is reduced by the same amount, then they take two more hours to meet. At what distance from P do the trains meet?

HI! Beat_gmat_09, You solved it with equation and get the result in the end that they will meet at the center point.

We know that the speed of both the trains are Same, So irrespective of the speed they will meet center, Take any two object's if the speed is same they will always meet at the center, It does not matter what time they take to travel the distance.

Yes, you are right, it's too obvious. I forgot to mention in my post.
No calculations are needed.

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goyalsau: Legendary Member; Posts: 866; Joined: Mon Aug 02, 2010 6:46 pm; Location: Gwalior, India; Thanked: 31 times

by goyalsau » Tue Dec 07, 2010 5:21 am

beat_gmat_09 wrote:
Yes, you are right, it's too obvious. I forgot to mention in my post.
No calculations are needed.

Then why the answer is not A, I am just not able to understand, Or it is a mistake.

Saurabh Goyal
[email protected]
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EveryBody Wants to Win But Nobody wants to prepare for Win.

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beat_gmat_09: Master | Next Rank: 500 Posts; Posts: 437; Joined: Sat Nov 22, 2008 5:06 amFollowed by: 1 member; Location: India; Thanked: 50 times; GMAT Score:580

by beat_gmat_09 » Tue Dec 07, 2010 5:54 am

@goyalsau : I'm extremely sorry, I was tried from work, and choose the wrong answer, realized my mistake after you pointed out !
Anyways, I too think it should be A.
what's the source ?
Do you have the OE ? If yes, then please post.

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goyalsau: Legendary Member; Posts: 866; Joined: Mon Aug 02, 2010 6:46 pm; Location: Gwalior, India; Thanked: 31 times

by goyalsau » Tue Dec 07, 2010 6:24 am

beat_gmat_09 wrote:@goyalsau : I'm extremely sorry, I was tried from work, and choose the wrong answer, realized my mistake after you pointed out !
Anyways, I too think it should be A.
what's the source ?
Do you have the OE ? If yes, then please post.

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Saurabh Goyal
[email protected]
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EveryBody Wants to Win But Nobody wants to prepare for Win.

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tomada: Master | Next Rank: 500 Posts; Posts: 406; Joined: Mon Jan 25, 2010 11:36 amFollowed by: 4 members; Location: Syracuse, NY; Thanked: 23 times; GMAT Score:740

by tomada » Tue Dec 07, 2010 8:10 am

Where was this question taken from? I agree with the other posters who feel that (A) is the correct answer. If (C) is the OA, can the original poster of this question please provide the source?

I'm really old, but I'll never be too old to become more educated.

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