Train A left Centerville station, heading towards Dale City : PS Archive
Check GMAT Club App Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

It is currently 07 Dec 2016, 11:48
GMAT Club Tests

Close

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
Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Train A left Centerville station, heading towards Dale City

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Manager
Manager
avatar
Joined: 21 May 2011
Posts: 239
Followers: 0

Kudos [?]: 198 [0], given: 8

Train A left Centerville station, heading towards Dale City [#permalink]

Show Tags

New post 12 Aug 2011, 14:26
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 6 sessions

HideShow timer Statistics

Train A left Centerville station, heading towards Dale City Station, at 3PM. Train B left Dale City Station, heading toward Centerville Station, at 3:20PM on the same day. The trains rode on straight tracks that were parallel to each other. If Train A traveled at a constant speed of 30 miles per hour and Train B traveled at a constant speed of 10 miles per hour, and the distance between the Centerville Station and Dale City Station is 90 miles, when did the trains meet each other?
Manager
Manager
User avatar
Joined: 14 Mar 2011
Posts: 203
Followers: 6

Kudos [?]: 113 [0], given: 21

Re: PS - 700 level - trains [#permalink]

Show Tags

New post 12 Aug 2011, 16:59
bschool83 wrote:
Train A left Centerville station, heading towards Dale City Station, at 3PM. Train B left Dale City Station, heading toward Centerville Station, at 3:20PM on the same day. The trains rode on straight tracks that were parallel to each other. If Train A traveled at a constant speed of 30 miles per hour and Train B traveled at a constant speed of 10 miles per hour, and the distance between the Centerville Station and Dale City Station is 90 miles, when did the trains meet each other?



From 3 Pm to 3:20 PM , train A will have travelled a distance of 20/60 * 30 = 10 miles. So at 3:20 distance remaining between train A and train B =80 miles.

Now let train A and train B meet x hours after 3:20. In x hours both trains will have travelled a total distance of 80 kms.

so, 30 X + 10X = 80

40x =80. there X =2

so trains will meet each other at 5:20.
Intern
Intern
User avatar
Status: If I play my cards right, I can work this to my advantage
Joined: 18 Jul 2011
Posts: 14
Location: India
Concentration: Operations, Social Entrepreneurship
GMAT Date: 11-12-2011
WE: Information Technology (Telecommunications)
Followers: 0

Kudos [?]: 4 [0], given: 11

Re: PS - 700 level - trains [#permalink]

Show Tags

New post 12 Aug 2011, 23:15
this is how i did it ...

let time be "t"
distance = speed * time
distance travelled by A = 30t
distance traveled by B = 10 ( t - 20/60) --- 20 mins later

distance traveled by A + distance traveled by B = 90
30t+ 10 (t-20/60) = 90

solving for t we'd get t= 7/3 = 2 and 1/3 = 2 h 20 mins
this when added to the original time 1500 hours would give the time reqd 1720
Manager
Manager
avatar
Joined: 21 May 2011
Posts: 239
Followers: 0

Kudos [?]: 198 [0], given: 8

Re: PS - 700 level - trains [#permalink]

Show Tags

New post 13 Aug 2011, 06:25
For those who want to learn a more strategic way to solve such problems:

If two objects start moving towards each other in straight line at the same time, their speeds add up. If moving away, subtract their speeds.

Therefore index the time to 3:20. In 20 minutes, A has moved 10 miles already.

So at 3:20, train A and train B are 80 miles apart. Their speeds together is 40 mph.
Therefore, they meet in 80/40 hrs = 2 hours.

Therefore at 5:20pm

Last edited by bschool83 on 13 Aug 2011, 06:46, edited 1 time in total.
Senior Manager
Senior Manager
avatar
Joined: 15 Feb 2011
Posts: 263
Followers: 4

Kudos [?]: 147 [0], given: 9

Re: PS - 700 level - trains [#permalink]

Show Tags

New post 13 Aug 2011, 06:39
bschool83 wrote:

So at 3:20, train A and train B are 80 miles apart. Their speeds together is 40 mph.
Therefore, they meet in 80/20 hrs = 2 hours.

Therefore at 5:20pm


Did you mean 80/40??
Manager
Manager
avatar
Joined: 21 May 2011
Posts: 239
Followers: 0

Kudos [?]: 198 [0], given: 8

Re: PS - 700 level - trains [#permalink]

Show Tags

New post 13 Aug 2011, 06:46
yes thanks for the correction. it's been changed.
Intern
Intern
avatar
Status: pursuing a dream
Joined: 02 Jun 2011
Posts: 45
Schools: MIT Sloan (LGO)
Followers: 1

Kudos [?]: 76 [0], given: 10

GMAT ToolKit User
Re: PS - 700 level - trains [#permalink]

Show Tags

New post 13 Aug 2011, 06:59
Train A equation: Xa = Xao + Sa·t

Train A has 20 minutes in advance, that's 1/3 hours, so 1/3 · 30 = 10.

Starting position, Xao = 10.

Xa = 10 + 30t

Train B equation: Xb = Xbo + Sb·t

Speed is negative since it's going in the opposite direction and starting position is 90 (starts at the end of the track).

Xb = 90 + (-10t)

Condition for meeting: Xa = Xb

10 + 30t = 90 - 10t

40t = 80

t = 2 hours (from 3:20) = 5:20.
GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 12886
Followers: 561

Kudos [?]: 158 [0], given: 0

Premium Member
Re: Train A left Centerville station, heading towards Dale City [#permalink]

Show Tags

New post 18 Dec 2015, 07:53
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Re: Train A left Centerville station, heading towards Dale City   [#permalink] 18 Dec 2015, 07:53
Display posts from previous: Sort by

Train A left Centerville station, heading towards Dale City

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.