GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video

 It is currently 29 May 2020, 13:17

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Two trains A and B starting from two points and travelling

 Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

### Hide Tags

Intern
Joined: 29 Oct 2013
Posts: 18
Two trains A and B starting from two points and travelling  [#permalink]

### Show Tags

18 Nov 2013, 07:48
5
00:00

Difficulty:

45% (medium)

Question Stats:

63% (02:20) correct 37% (02:08) wrong based on 37 sessions

### HideShow timer Statistics

Two trains A and B starting from two points and travelling in opposite directions, reach their destinations 9 hours and 4 hours respectively after meeting each other. If the train A travels at 80kmph, find the rate at which the train B runs.

(A) 40
(B) 60
(C) 120
(D) 80
(E) 100

Posted from my mobile device
Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 10477
Location: Pune, India
Re: Two trains A and B starting from two points and travelling  [#permalink]

### Show Tags

18 Nov 2013, 20:38
1
1
fra wrote:
Two trains A and B starting from two points and travelling in opposite directions, reach their destinations 9 hours and 4 hours respectively after meeting each other. If the train A travels at 80kmph, find the rate at which the train B runs.

(A) 40
(B) 60
(C) 120
(D) 80
(E) 100

Posted from my mobile device

Using Formula:

If two objects A and B start simultaneously from opposite points and, after meeting, reach their destinations in ‘a’ and ‘b’ hours respectively (i.e. A takes ‘a hrs’ to travel from the meeting point to his destination and B takes ‘b hrs’ to travel from the meeting point to his destination), then the ratio of their speeds is given by:
Sa/Sb = √(b/a)
i.e. Ratio of speeds is given by the square root of the inverse ratio of time taken.
Sa/Sb = √(4/9) = 2/3

This gives us that the ratio of the speed of A : speed of B as 2:3.
Since speed of A is 80 kmph, speed of B must be 80*(3/2) = 120 kmph

You can also do this question without using the formula. Check out this post for the method: http://www.veritasprep.com/blog/2013/04 ... -formulas/
_________________
Karishma
Veritas Prep GMAT Instructor

Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >
Manager
Joined: 25 Oct 2013
Posts: 138
Re: Two trains A and B starting from two points and travelling  [#permalink]

### Show Tags

19 Nov 2013, 01:55
1
VeritasPrepKarishma wrote:
fra wrote:
Two trains A and B starting from two points and travelling in opposite directions, reach their destinations 9 hours and 4 hours respectively after meeting each other. If the train A travels at 80kmph, find the rate at which the train B runs.

(A) 40
(B) 60
(C) 120
(D) 80
(E) 100

Posted from my mobile device

Using Formula:

If two objects A and B start simultaneously from opposite points and, after meeting, reach their destinations in ‘a’ and ‘b’ hours respectively (i.e. A takes ‘a hrs’ to travel from the meeting point to his destination and B takes ‘b hrs’ to travel from the meeting point to his destination), then the ratio of their speeds is given by:
Sa/Sb = √(b/a)
i.e. Ratio of speeds is given by the square root of the inverse ratio of time taken.
Sa/Sb = √(4/9) = 2/3

This gives us that the ratio of the speed of A : speed of B as 2:3.
Since speed of A is 80 kmph, speed of B must be 80*(3/2) = 120 kmph

You can also do this question without using the formula. Check out this post for the method: http://www.veritasprep.com/blog/2013/04 ... -formulas/

Can you please explain this a little more?

First, nothing is given in the question as to what are the destinations of each train. Are we to assume that the starting point of A is destination of B and vice-versa?

Second, the question also doesn't say whether the trains started at the same time, can we just assume that they did?
Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 10477
Location: Pune, India
Re: Two trains A and B starting from two points and travelling  [#permalink]

### Show Tags

19 Nov 2013, 07:57
gmatprav wrote:
VeritasPrepKarishma wrote:
fra wrote:
Two trains A and B starting from two points and travelling in opposite directions, reach their destinations 9 hours and 4 hours respectively after meeting each other. If the train A travels at 80kmph, find the rate at which the train B runs.

(A) 40
(B) 60
(C) 120
(D) 80
(E) 100

Posted from my mobile device

Using Formula:

If two objects A and B start simultaneously from opposite points and, after meeting, reach their destinations in ‘a’ and ‘b’ hours respectively (i.e. A takes ‘a hrs’ to travel from the meeting point to his destination and B takes ‘b hrs’ to travel from the meeting point to his destination), then the ratio of their speeds is given by:
Sa/Sb = √(b/a)
i.e. Ratio of speeds is given by the square root of the inverse ratio of time taken.
Sa/Sb = √(4/9) = 2/3

This gives us that the ratio of the speed of A : speed of B as 2:3.
Since speed of A is 80 kmph, speed of B must be 80*(3/2) = 120 kmph

You can also do this question without using the formula. Check out this post for the method: http://www.veritasprep.com/blog/2013/04 ... -formulas/

Can you please explain this a little more?

First, nothing is given in the question as to what are the destinations of each train. Are we to assume that the starting point of A is destination of B and vice-versa?

Second, the question also doesn't say whether the trains started at the same time, can we just assume that they did?

The intent of the question is quite clear - the execution sure is lacking. In my post, I have explicitly mentioned both points as they will be in an actual GMAT question too.
_________________
Karishma
Veritas Prep GMAT Instructor

Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >
Manager
Joined: 25 Oct 2013
Posts: 138
Re: Two trains A and B starting from two points and travelling  [#permalink]

### Show Tags

19 Nov 2013, 09:00
VeritasPrepKarishma wrote:

The intent of the question is quite clear - the execution sure is lacking. In my post, I have explicitly mentioned both points as they will be in an actual GMAT question too.

Hello Karishma thanks for the reply. Yes, I checked your link and it is very clear about the destinations, the current question was not. I also arrived at the same answer going purely by the intent I wanted to make sure I am not assuming something that is not stated in the question. Glad to know the real GMAT will not have this kind of ambiguity.
Re: Two trains A and B starting from two points and travelling   [#permalink] 19 Nov 2013, 09:00

# Two trains A and B starting from two points and travelling

 Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne