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# Trains A and B which were originally 420 miles apart began traveling

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Intern
Joined: 24 Feb 2016
Posts: 27
Location: India
Schools: LBS (A)
GMAT 1: 650 Q45 V34
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Trains A and B which were originally 420 miles apart began traveling  [#permalink]

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26 Aug 2016, 13:08
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Question Stats:

83% (00:26) correct 17% (00:56) wrong based on 52 sessions

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Trains A and B which were originally 420 miles apart began traveling towards one another on parallel adjacent tracks. How many miles from the point where train A began to travel will the trains meet?

(1) Train A is traveling at a constant speed of 94 miles per hour and train B is traveling at a constant speed of 47 miles per hour.

(2) Train A is traveling at a constant speed that is twice the constant speed of train B.

OA after discussion

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Manager
Joined: 04 Feb 2012
Posts: 134
Location: India
GPA: 3.96
WE: Research (Pharmaceuticals and Biotech)
Re: Trains A and B which were originally 420 miles apart began traveling  [#permalink]

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26 Aug 2016, 13:34
Assuming their time of travel will be same (meeting condition DST problem) We need to know the distance covered by each and equate times Because essentially they must have travelled for the same "time" speed alone will not work!
Both statement A and B give speed but no mention on the time travelled or d=20istance.

So i think the answer should be E

Only distance given is the 420 miles which would be combined distance (dA+dB); hence I would go with E

please let me know If i am missing something
Intern
Joined: 24 Feb 2016
Posts: 27
Location: India
Schools: LBS (A)
GMAT 1: 650 Q45 V34
GPA: 4
Trains A and B which were originally 420 miles apart began traveling  [#permalink]

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26 Aug 2016, 14:59
HBSdetermined wrote:
Assuming their time of travel will be same (meeting condition DST problem) We need to know the distance covered by each and equate times Because essentially they must have travelled for the same "time" speed alone will not work!
Both statement A and B give speed but no mention on the time travelled or d=20istance.

So i think the answer should be E

Only distance given is the 420 miles which would be combined distance (dA+dB); hence I would go with E

please let me know If i am missing something

This is the explanation provided by kaplan
i spent good 15 minutes on this and could not understand what the answer was trying to say.
Analyze the Question Stem:

Here we have a Data Sufficiency Value question. Remember that a Statement that allows us to solve for a single value as the solution to this problem is considered Sufficient. A statement that results in multiple possible solutions is considered Insufficient.

From the given information in the question, we know that Trains A and B were originally 420 miles apart. We are asked how many miles will it be from the point of origin of A to the point where the trains meet. In order to solve, we will need to know the speed of A and B.

Evaluate the Statements:

Statement (1): Statement (1) tells us the rates of both trains. We can calculate when they would meet by setting them equal to each other using the formula: distance = rate × time. Therefore, Statement (1) is Sufficient. Eliminate choices (B), (C) and (E).

Note that solving is not necessary to determine the sufficiency of the statement. In Data Sufficiency, all we need is the knowledge that we have enough information to do so. This is how these questions can be answered in most cases more quickly than Problem Solving questions.

Statement (2): Statement 2 gives us the proportional relationship between the speeds of the two trains. This is enough information to use the distance formula (distance = rate × time) to calculate when they would meet by setting them equal to each other.

Note again that solving is not necessary to determine the sufficiency of the statement. In Data Sufficiency, all we need is the knowledge that we have enough information to do so. Therefore, Statement (2) is Sufficient. We could use this information to figure out when the trains would meet and how far A is from its original starting point, so Answer Choice (D) is correct.

Combined: Unnecessary
Manager
Joined: 04 Feb 2012
Posts: 134
Location: India
GPA: 3.96
WE: Research (Pharmaceuticals and Biotech)
Re: Trains A and B which were originally 420 miles apart began traveling  [#permalink]

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26 Aug 2016, 15:13
If someone could actually solve it correctly I can understand where am I missing in my logic!

Posted from my mobile device
Manager
Joined: 03 Jul 2016
Posts: 76
Re: Trains A and B which were originally 420 miles apart began traveling  [#permalink]

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26 Aug 2016, 15:21
1
1
achintsodhi wrote:
HBSdetermined wrote:
Assuming their time of travel will be same (meeting condition DST problem) We need to know the distance covered by each and equate times Because essentially they must have travelled for the same "time" speed alone will not work!
Both statement A and B give speed but no mention on the time travelled or d=20istance.

So i think the answer should be E

Only distance given is the 420 miles which would be combined distance (dA+dB); hence I would go with E

please let me know If i am missing something

This is the explanation provided by kaplan
i spent good 15 minutes on this and could not understand what the answer was trying to say.
Analyze the Question Stem:

Here we have a Data Sufficiency Value question. Remember that a Statement that allows us to solve for a single value as the solution to this problem is considered Sufficient. A statement that results in multiple possible solutions is considered Insufficient.

From the given information in the question, we know that Trains A and B were originally 420 miles apart. We are asked how many miles will it be from the point of origin of A to the point where the trains meet. In order to solve, we will need to know the speed of A and B.

Evaluate the Statements:

Statement (1): Statement (1) tells us the rates of both trains. We can calculate when they would meet by setting them equal to each other using the formula: distance = rate × time. Therefore, Statement (1) is Sufficient. Eliminate choices (B), (C) and (E).

Note that solving is not necessary to determine the sufficiency of the statement. In Data Sufficiency, all we need is the knowledge that we have enough information to do so. This is how these questions can be answered in most cases more quickly than Problem Solving questions.

Statement (2): Statement 2 gives us the proportional relationship between the speeds of the two trains. This is enough information to use the distance formula (distance = rate × time) to calculate when they would meet by setting them equal to each other.

Note again that solving is not necessary to determine the sufficiency of the statement. In Data Sufficiency, all we need is the knowledge that we have enough information to do so. Therefore, Statement (2) is Sufficient. We could use this information to figure out when the trains would meet and how far A is from its original starting point, so Answer Choice (D) is correct.

Combined: Unnecessary

Assuming that you are clear about Statement 1, here is the explanation for how statement 2 is sufficient.

Assume,
t hrs is the time taken for Train A to meet a moving Train B.
x miles/hr is the speed of Train B. Therefore, 2x is the speed of Train A.
d is the distance travelled by Train A in t hrs. Therefore, (420-d) is the distance travelled by Train B in the same t hrs.

Now,
d = 2x * t ---> 1
(420-d) = x * t --> 2

2/1 => (420-d)/d = 1/2. We can solve for d.

Hence D.
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Joined: 09 Sep 2013
Posts: 7319
Re: Trains A and B which were originally 420 miles apart began traveling  [#permalink]

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12 Oct 2017, 04:35
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Re: Trains A and B which were originally 420 miles apart began traveling &nbs [#permalink] 12 Oct 2017, 04:35
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