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# Trains A and B travel at the same constant rate in opposite

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Manager
Joined: 23 Oct 2012
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Trains A and B travel at the same constant rate in opposite  [#permalink]

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15 Aug 2013, 11:04
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Difficulty:

95% (hard)

Question Stats:

43% (01:14) correct 57% (01:33) wrong based on 635 sessions

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Trains A and B travel at the same constant rate in opposite directions along the same route between Town G and Town H. If, after traveling for 2 hours, Train A passes Train B, how long does it take Train B to travel the entire distance between Town G and Town H?

(1) Train B started traveling between Town G and Town H 1 hour after Train A started traveling between Town H and Town G.

(2) Train B travels at the rate of 150 miles per hour.

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Director
Joined: 14 Dec 2012
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Location: India
Concentration: General Management, Operations
GMAT 1: 700 Q50 V34
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Re: Trains A and B travel at the same constant rate in opposite  [#permalink]

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15 Aug 2013, 11:18
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2
2013gmat wrote:
Trains A and B travel at the same constant rate in opposite directions along the same route between Town G and Town H. If, after traveling for 2 hours, Train A passes Train B, how long does it take Train B to travel the entire distance between Town G and Town H?

(1) Train B started traveling between Town G and Town H 1 hour after Train A started traveling between Town H and Town G.

(2) Train B travels at the rate of 150 miles per hour.

plz explain.

just note: A and B have same speed.
train A travelled for 2 hours before they met.

statement 1:
train B Started 1 hour late therefore first he travelled for 1 hour before both train met.
now since both train have same speed then it means train B will also take 2 hours to complete remaining distance...hence total time = 2+1 =3 hrs
hence sufficient.

(2) Train B travels at the rate of 150 miles per hour.
now we dont know whether both train started together or anyone started late.
hence insufficient.

hence A
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##### General Discussion
Manager
Joined: 15 Aug 2013
Posts: 56
Re: Trains A and B travel at the same constant rate in opposite  [#permalink]

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16 Aug 2013, 08:12
1
Hi,
For option 2, why cant we assume both trains started simultaneouly since the question would then be -
Trains A and B travel at the same constant rate in opposite directions along the same route between Town G and Town H. If, after traveling for 2 hours, Train A passes Train B, how long does it take Train B to travel the entire distance between Town G and Town H?
Train B travels at the rate of 150 miles per hour.

If this comes in PS - w ecould have solved this easily by saying both the trains travelled for 2 hrs with speed 150m/h. Hence the toal distance will be 150*2 + 150*2 = 600; or train B took 4 hrs.. Or simply Train A and B travelled for 2 hrs each, so 4 hours.
I am confused why cant we do this way..?
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Re: Trains A and B travel at the same constant rate in opposite  [#permalink]

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16 Aug 2013, 11:13
i agree with zerosleep.
since the statement two or the question stem does not mention whether the two trains started simultaneously or at different timings, cant we presume they started together?
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Re: Trains A and B travel at the same constant rate in opposite  [#permalink]

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16 Aug 2013, 11:22
1
1
semwal wrote:
i agree with zerosleep.
since the statement two or the question stem does not mention whether the two trains started simultaneously or at different timings, cant we presume they started together?

hi semwal.

until and unless it is not specifically stated in the argument that they have not started at same time you cant assume so.
moreover in such cases most of the time you will get hint from one of the statement as in this case in statement 1 it clearly says that both have not started at same time.
never assume anything.
this is GMAT ..it will not confuse you in such things...so never assume anything.

hope it helps
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Joined: 06 Apr 2011
Posts: 13
Re: Trains A and B travel at the same constant rate in opposite  [#permalink]

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10 Nov 2013, 13:43
1
logic driven question hardly any calculation involved.
the key is "same constant speed" in the question stem, once deciphered everything should fall apart. Make a grid to get a more visual understanding

B can be rejected out rightly. A is the answer.
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Re: Trains A and B travel at the same constant rate in opposite  [#permalink]

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20 Jan 2015, 02:37
blueseas wrote:
2013gmat wrote:
Trains A and B travel at the same constant rate in opposite directions along the same route between Town G and Town H. If, after traveling for 2 hours, Train A passes Train B, how long does it take Train B to travel the entire distance between Town G and Town H?

(1) Train B started traveling between Town G and Town H 1 hour after Train A started traveling between Town H and Town G.

(2) Train B travels at the rate of 150 miles per hour.

plz explain.

just note: A and B have same speed.
train A travelled for 2 hours before they met.

statement 1:
train B Started 1 hour late therefore first he travelled for 1 hour before both train met.
now since both train have same speed then it means train B will also take 2 hours to complete remaining distance...hence total time = 2+1 =3 hrs
hence sufficient.

(2) Train B travels at the rate of 150 miles per hour.
now we dont know whether both train started together or anyone started late.
hence insufficient.

hence A

Doesn't this statement assume that A traveled for 2 hours starting from one of the towns?
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Re: Trains A and B travel at the same constant rate in opposite  [#permalink]

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20 Jan 2015, 05:48
2
nayanprateek wrote:
blueseas wrote:
2013gmat wrote:
Trains A and B travel at the same constant rate in opposite directions along the same route between Town G and Town H. If, after traveling for 2 hours, Train A passes Train B, how long does it take Train B to travel the entire distance between Town G and Town H?

(1) Train B started traveling between Town G and Town H 1 hour after Train A started traveling between Town H and Town G.

(2) Train B travels at the rate of 150 miles per hour.

plz explain.

just note: A and B have same speed.
train A travelled for 2 hours before they met.

statement 1:
train B Started 1 hour late therefore first he travelled for 1 hour before both train met.
now since both train have same speed then it means train B will also take 2 hours to complete remaining distance...hence total time = 2+1 =3 hrs
hence sufficient.

(2) Train B travels at the rate of 150 miles per hour.
now we dont know whether both train started together or anyone started late.
hence insufficient.

hence A

Doesn't this statement assume that A traveled for 2 hours starting from one of the towns?

G _____________________________ H
A --->....................................<---B

After 2 hrs of A's traveling and 1 hr of B's traveling:

G______________________________ H
----------------------------AB-----------

A took 2 hrs to cover the red dotted line distance as given in the question. B will also take 2 hrs to cover this distance. Hence total time taken by B will be 1 + 2 = 3 hrs
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Joined: 09 Jul 2013
Posts: 1
Re: Trains A and B travel at the same constant rate in opposite  [#permalink]

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03 Aug 2016, 09:27
without a and b, we know either train can cover the whole route in 4hours. hate this kinda questions... hehe
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Joined: 02 Apr 2014
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Trains A and B travel at the same constant rate in opposite  [#permalink]

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18 Sep 2017, 20:47
Hi Karishma,

I initially answered E, misunderstood the statement "Trains A and B travel at the same constant rate" in the question, I assumed that A and B travel at their same constant speeds, but they could travel at diff speed but still maintain their respective speed constant. can this statement mean so?. This kind of wordings confuses me.

Yes if Speed of A and B is same, then answer is A.
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Re: Trains A and B travel at the same constant rate in opposite  [#permalink]

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18 Sep 2017, 22:41
hellosanthosh2k2 wrote:
Hi Karishma,

I initially answered E, misunderstood the statement "Trains A and B travel at the same constant rate" in the question, I assumed that A and B travel at their same constant speeds, but they could travel at diff speed but still maintain their respective speed constant. can this statement mean so?. This kind of wordings confuses me.

Yes if Speed of A and B is same, then answer is A.

Note that we are talking about a single constant rate:
"Trains A and B travel at the same constant rate..."

So they must have the same rate. Else they would be travelling at their own constant rates.
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Senior Manager
Joined: 14 Dec 2017
Posts: 471
Re: Trains A and B travel at the same constant rate in opposite  [#permalink]

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15 Jun 2018, 08:02
2013gmat wrote:
Trains A and B travel at the same constant rate in opposite directions along the same route between Town G and Town H. If, after traveling for 2 hours, Train A passes Train B, how long does it take Train B to travel the entire distance between Town G and Town H?

(1) Train B started traveling between Town G and Town H 1 hour after Train A started traveling between Town H and Town G.

(2) Train B travels at the rate of 150 miles per hour.

Lets say the speed of the two trains is = a miles per hour,

the distance between the two towns as D miles.

Since the two trains travel in opposite direction, their relative speed = a + a = 2a miles per hour

Total time of travel till they pass each other = 2 hours & we are asked to find time taken for train B to travel the whole distance = D/a

Statement 1:
Train B started traveling between Town G and Town H 1 hour after Train A started traveling between Town H and Town G

Hence we have train A traveled alone for 1 hour, covering distance = a * 1 = a miles

Distance left to travel = (D - a) miles

After 1 hour both trains are traveling towards each other & meet each other after 1 hour,

Hence we have, (D - a) = 2a * 1 = 2a

D = 3a or D/a = 3

Hence Statement 1 alone is Sufficient.

Statement 2:

Train B travels at the rate of 150 miles per hour.

Hence a = 150 miles per hour, but no information about the distance traveled.

Statement 2 alone is Not Sufficient.

Thanks,
GyM
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Re: Trains A and B travel at the same constant rate in opposite &nbs [#permalink] 15 Jun 2018, 08:02
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