A bus from city M is traveling to city N at a constant speed : GMAT Problem Solving (PS)
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 22 Jan 2017, 09:18

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# A bus from city M is traveling to city N at a constant speed

Author Message
TAGS:

### Hide Tags

Senior Manager
Joined: 18 Aug 2009
Posts: 303
Followers: 3

Kudos [?]: 272 [5] , given: 9

A bus from city M is traveling to city N at a constant speed [#permalink]

### Show Tags

07 Nov 2009, 02:23
5
KUDOS
46
This post was
BOOKMARKED
00:00

Difficulty:

95% (hard)

Question Stats:

34% (03:47) correct 66% (02:28) wrong based on 700 sessions

### HideShow timer Statistics

A bus from city M is traveling to city N at a constant speed while another bus is making the same journey in the opposite direction at the same constant speed. They meet in point P after driving for 2 hours. The following day the buses do the return trip at the same constant speed. One bus is delayed 24 minutes and the other leaves 36 minutes earlier. If they meet 24 miles from point P, what is the distance between the two cities?

A. 48
B. 72
C. 96
D. 120
E. 192

The source is GMATClub's diagnostic test... would look forward to see some innovative approach to this.
Thanks!
[Reveal] Spoiler: OA

Last edited by Bunuel on 27 Feb 2012, 23:01, edited 1 time in total.
Edited the question
Senior Manager
Joined: 31 Aug 2009
Posts: 419
Location: Sydney, Australia
Followers: 8

Kudos [?]: 276 [4] , given: 20

### Show Tags

07 Nov 2009, 03:13
4
KUDOS
2
This post was
BOOKMARKED
Hmmm I did this question a while ago and got it wrong so trying again

Rate x time = distance.
For the initial trip lets the distance to the midpoint be represented by P.
EQN1: R x 2 = P

For the second trip we know one bus left late and one left early. Together this is just a tricky way of saying one bus left an hour after the other. We know the total trip takes 4 hours (since getting to P is 2 hours). The second trip can be represented by:

Since the trip takes 4 hours if a bus leaves one hour early, the reminaining 3 hours are split between the two buses, ie. 1 + 3/2 = 2.5
EQN2: R x 2.5 = P + 24

EQN2-EQN1 : 0.5R=24
R=48

So the distance is rate x time = 48 x 4 = 192.
ANS = E
Director
Joined: 01 Apr 2008
Posts: 897
Name: Ronak Amin
Schools: IIM Lucknow (IPMX) - Class of 2014
Followers: 28

Kudos [?]: 648 [6] , given: 18

### Show Tags

07 Nov 2009, 03:35
6
KUDOS
1
This post was
BOOKMARKED
Normally I goof up with distance-speed probs, but got this one right.

here, B1 and B2 are coming towards each other at the same speed, so when they meet they MUST have traveled the same distance.
in 2 hours B1 has traveled 2S miles ( let S be the speed )
so, B2 has also traveled 2S miles

So we have a line segment MN having a distance 4S and PM=MN = 2S. Divide this line segment into four parts with each having distance S.

Okay, for the second trip the total time delay is 60 mins=1 hour. Suppose B2(at N) starts early. In this one hour B2 has traveled S miles. At this time B1 will start and both buses will meet at a point which is halfway of the remaining distance(3S) = 3S/2.

Now, 2S (which represents PM) - 3S/2 (second trip's halfway meeting point) = 12 => S=48.
So, total distance = 4S = 4*48 = 192.
Intern
Affiliations: CA - India
Joined: 27 Oct 2009
Posts: 45
Location: India
Schools: ISB - Hyderabad, NSU - Singapore
Followers: 20

Kudos [?]: 694 [0], given: 5

### Show Tags

07 Nov 2009, 05:45
I am not sure if I am right, but my ans differs from the 2 posted earlier. I think the distance between M and N should be 96.

Facts given: Both buses travel at the same speed. When they leave at exactly same time from M and N respectively, they meet at P in 2 hours. This means the total journey should be taking 4 hours for both of them individually.

Now, one bus leaves 36 min earlier and other one is delayed by 24 min, there is a total gap of 60 min or 1 hour between the two buses. If their meeting point is now shifted by 24 miles, it means their respective speeds are 24 miles an hour. This drives me to a conclusion that the totla distance between M and N should be 4 * 24 = 96 miles.

Please correct me if i'm wrong!!
Senior Manager
Joined: 18 Aug 2009
Posts: 303
Followers: 3

Kudos [?]: 272 [7] , given: 9

### Show Tags

07 Nov 2009, 07:45
7
KUDOS
I am not sure if I am right, but my ans differs from the 2 posted earlier. I think the distance between M and N should be 96.

Facts given: Both buses travel at the same speed. When they leave at exactly same time from M and N respectively, they meet at P in 2 hours. This means the total journey should be taking 4 hours for both of them individually.

Now, one bus leaves 36 min earlier and other one is delayed by 24 min, there is a total gap of 60 min or 1 hour between the two buses. If their meeting point is now shifted by 24 miles, it means their respective speeds are 24 miles an hour. This drives me to a conclusion that the totla distance between M and N should be 4 * 24 = 96 miles.

Please correct me if i'm wrong!!

Dear Economist and yangsta8, thanks for the new approaches... i still am spinning though
kalpesh, following is the official explanation which I spent some time to understand (24miles in 30mins):

(I didn't know that these questions have their own thread, sorry for repost)
gmat-diagnostic-test-question-79354.html
The buses travel at the same constant speed. It would take one bus to travel 4 hours to cover the distance between the cities M and N (two buses drove for 2 hours each). We need to find the speed of the bus. If the first bus was delayed by 24 minutes and the second one left 36 minutes earlier, it makes the second bus $$24+36=60$$ minutes ahead of the first bus.

The meeting point was 24 miles away on this second day. We know the distance difference between the two meeting points, but we also need to find difference in time those 24 miles were covered. If the second bus drove for 1 hour before the first one departed, each of them had to go for another 1.5 hour to meet (1.5 hour + 1.5 hour + 1 hour). The second bus traveled for 2.5 hours and the first one for 1.5 hour. Therefore the meeting point on the second day was 30 minutes away from that of the previous day.

So the second bus covered 24 miles in 30 minutes, which gives us the speed of the bus, 48 mph. We can calculate the distance as we already know the speed:

$$4*48=192$$ miles.
Math Expert
Joined: 02 Sep 2009
Posts: 36598
Followers: 7094

Kudos [?]: 93453 [25] , given: 10563

### Show Tags

07 Nov 2009, 08:02
25
KUDOS
Expert's post
22
This post was
BOOKMARKED
A bus from city M is traveling to city N at a constant speed while another bus is making the same journey in the opposite direction at the same constant speed. They meet in point P after driving for 2 hours. The following day the buses do the return trip at the same constant speed. One bus is delayed 24 minutes and the other leaves 36 minutes earlier. If they meet 24 miles from point P, what is the distance between the two cities?

A. 48
B. 72
C. 96
D. 120
E. 192

Distance between the cities $$d$$.

First meeting point $$\frac{d}{2}$$, as both buses travel at the same constant speed and leave the cities same time they meet at the halfway.

Total time to cover the $$d$$ 4 hours, as the buses meet in 2 hours.

On the second day first bus traveled alone 1 hour (36min +24min), hence covered $$0.25d$$, and $$0.75d$$ is left cover.

They meet again at the halfway of $$0.75d$$, which is 24 miles from $$\frac{d}{2}$$:

$$\frac{d}{2}-24=\frac{0.75d}{2}$$

$$d=192$$

_________________
Joined: 31 Dec 1969
Location: Russian Federation
Concentration: Technology, Entrepreneurship
GMAT 1: 710 Q49 V0
GMAT 2: 700 Q V
GMAT 3: 740 Q40 V50
GMAT 4: 700 Q48 V38
GMAT 5: 710 Q45 V41
GMAT 6: 680 Q47 V36
GMAT 7: Q42 V44
GMAT 8: Q42 V44
GMAT 9: 740 Q49 V42
GMAT 10: 740 Q V
GMAT 11: 500 Q47 V33
GMAT 12: 670 Q V
WE: Engineering (Manufacturing)
Followers: 0

Kudos [?]: 202 [4] , given: 102262

### Show Tags

29 Mar 2011, 19:29
4
KUDOS
Bunuel wrote:
Distance between the cities $$d$$.

First meeting point $$\frac{d}{2}$$, as both buses travel at the same constant speed and leave the cities same time they meet at the halfway.

Total time to cover the $$d$$ 4 hours, as the buses meet in 2 hours.

On the second day first bus traveled alone 1 hour (36min +24min), hence covered $$0.25d$$, and $$0.75d$$ is left cover.

They meet again at the halfway of $$0.75d$$, which is 24 miles from $$\frac{d}{2}$$:

$$\frac{d}{2}-24=\frac{0.75d}{2}$$

$$d=192$$

This is the only explanation that made sense to me! Thanks!! +1
SVP
Joined: 16 Nov 2010
Posts: 1672
Location: United States (IN)
Concentration: Strategy, Technology
Followers: 33

Kudos [?]: 514 [3] , given: 36

### Show Tags

29 Mar 2011, 20:41
3
KUDOS
1
This post was
BOOKMARKED
M----------x------ P-----(d-x)--------N

2v + 2v = d

x = 2v (they meet at halfway)

Next day they meet at x - 24 miles from city M

d/2v = 2 -> On day 1

Next day, in 1 hr, B2 travels v distance = d/4 miles, and then it travels (24 miles + d/4) from there for t hrs at speed v where it meets B1 (B1 has also traveled for t hrs by then)

(24+ d/4)/v = (d/2-24)/v

=> 48 = d/2 - d/4

=> d = 4 * 48 = 192

_________________

Formula of Life -> Achievement/Potential = k * Happiness (where k is a constant)

GMAT Club Premium Membership - big benefits and savings

Intern
Joined: 20 Oct 2011
Posts: 5
Followers: 0

Kudos [?]: 0 [0], given: 3

### Show Tags

25 Oct 2011, 14:47
Thanks Bunuel.

Your explanation is very clear ... I also has trouble undersatnding the official answer..
Kudos to you!
Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7125
Location: Pune, India
Followers: 2138

Kudos [?]: 13691 [14] , given: 222

### Show Tags

27 Oct 2011, 05:15
14
KUDOS
Expert's post
4
This post was
BOOKMARKED
gmattokyo wrote:
A bus from city M is traveling to city N at a constant speed while another bus is making the same journey in the opposite direction at the same constant speed. They meet in point P after driving for 2 hours. The following day the buses do the return trip at the same constant speed. One bus is delayed 24 minutes and the other leaves 36 minutes earlier. If they meet 24 miles from point P, what is the distance between the two cities?

* 48
* 72
* 96
* 120
* 192

The source is GMATClub's diagnostic test... would look forward to see some innovative approach to this.
Thanks!

A little bit of visualization can help you solve this question in a moment. Look at the diagram below. Since they travel at same speed for 2 hrs, point P must be right in the middle of M and N.
Attachment:

Ques3.jpg [ 13.29 KiB | Viewed 15808 times ]

On the return trip, the following is what happens. One bus starts at 11:24 and reaches P at 1:24. The other bus starts at 12:24 and reaches mid way between P and N at 1:24 (in one hour, it covers half of the distance it usually covers in 2 hrs). At 1:24, both buses have a fourth of the total distance between them. They will both cover equal distances and meet at a point which is 1/8th of the total distance from P. This distance is given as 24 miles. Hence total distance = 24*8 = 192 miles
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199 Veritas Prep Reviews Current Student Joined: 21 Aug 2010 Posts: 210 Followers: 2 Kudos [?]: 17 [0], given: 28 Re: two buses, same speed... head spinning [#permalink] ### Show Tags 27 Oct 2011, 11:12 Karishma you are a champ Senior Manager Joined: 11 May 2011 Posts: 372 Location: US Followers: 3 Kudos [?]: 95 [1] , given: 46 Re: two buses, same speed... head spinning [#permalink] ### Show Tags 27 Oct 2011, 11:33 1 This post received KUDOS @Bunuel - Very neat explanation. Kudos to you..!! _________________ ----------------------------------------------------------------------------------------- What you do TODAY is important because you're exchanging a day of your life for it! ----------------------------------------------------------------------------------------- Senior Manager Joined: 13 May 2011 Posts: 317 WE 1: IT 1 Yr WE 2: Supply Chain 5 Yrs Followers: 21 Kudos [?]: 252 [5] , given: 11 Re: two buses, same speed... head spinning [#permalink] ### Show Tags 09 Dec 2011, 03:39 5 This post received KUDOS Fro those of you who are dependent on MGMAT RTD chart (as i am) can try the following: From the attached chart#2 P=R(T+3/5)-24 P=R(T-2/5)+24 Therefore, R(T+3/5)-24=R(T-2/5)+24 Solving for R, we get Rate=48 m/h Plug in value in Chart#1: p=96 So, D=192 Attachments RTD.gif [ 3.18 KiB | Viewed 15100 times ] Intern Joined: 31 Oct 2011 Posts: 47 Location: India Followers: 0 Kudos [?]: 15 [0], given: 11 Re: two buses, same speed... head spinning [#permalink] ### Show Tags 19 Dec 2011, 01:46 Good exp by Bunuel _________________ Regards, Rajesh Helping hands are anytime better than praying hearts Kudos ???!@#$\$ !!! I just love them

Manager
Joined: 26 Apr 2011
Posts: 228
Followers: 2

Kudos [?]: 2 [0], given: 14

### Show Tags

19 Dec 2011, 02:04
quite confusing question but very good explained by bynnel and karishma
thanks to both of you
Intern
Joined: 16 Dec 2011
Posts: 49
GMAT Date: 04-23-2012
Followers: 0

Kudos [?]: 6 [0], given: 12

### Show Tags

30 Dec 2011, 01:14
good explanation bunuel.......... thanks
Director
Joined: 28 Jul 2011
Posts: 563
Location: United States
GPA: 3.86
WE: Accounting (Commercial Banking)
Followers: 3

Kudos [?]: 212 [0], given: 16

### Show Tags

30 Dec 2011, 06:20
good challenging question and an amazing explanation by karishma
_________________

CEO
Status: Nothing comes easy: neither do I want.
Joined: 12 Oct 2009
Posts: 2795
Location: Malaysia
Concentration: Technology, Entrepreneurship
Schools: ISB '15 (M)
GMAT 1: 670 Q49 V31
GMAT 2: 710 Q50 V35
Followers: 226

Kudos [?]: 1622 [0], given: 235

### Show Tags

01 Jan 2012, 09:28
suppose total distance = 2d and point p is at d distance from M and N.

for bus M
d+24 = v(1+36/60) = 1.6v

for bus N
d-24 = v(1-24/60) = 0.6v

subtract them, we get v=48

final distance = 2v*t = 4v =192 ( final distance = 2vt because relative speed = v1+v2 = 2v)
_________________

Fight for your dreams :For all those who fear from Verbal- lets give it a fight

Money Saved is the Money Earned

Jo Bole So Nihaal , Sat Shri Akaal

GMAT Club Premium Membership - big benefits and savings

Gmat test review :
http://gmatclub.com/forum/670-to-710-a-long-journey-without-destination-still-happy-141642.html

Intern
Joined: 05 Aug 2011
Posts: 13
Followers: 0

Kudos [?]: 0 [0], given: 6

### Show Tags

27 Feb 2012, 22:03
Bunuel wrote:
$$\frac{d}{2}-24=\frac{0.75d}{2}$$

why do you assume -24 instead of +24?
Math Expert
Joined: 02 Sep 2009
Posts: 36598
Followers: 7094

Kudos [?]: 93453 [0], given: 10563

### Show Tags

27 Feb 2012, 22:36
T740qc wrote:
Bunuel wrote:
$$\frac{d}{2}-24=\frac{0.75d}{2}$$

why do you assume -24 instead of +24?

You can derive this either my reasoning or simply by noticing that d/2>0.75d/2, so it should be d/2-24=0.75d/2 (greater value minus 24 equals to smaller value).

Hope it's clear,
_________________
Re: two buses, same speed... head spinning   [#permalink] 27 Feb 2012, 22:36

Go to page    1   2    Next  [ 34 posts ]

Similar topics Replies Last post
Similar
Topics:
A train traveled from City A to City B without stopping 1 23 Aug 2016, 13:21
8 Anne traveled from City A to City B in 4 hours, and her speed was betw 10 25 Aug 2015, 23:07
9 A bus traveled from its depot to its destination at an average speed 12 15 Jul 2015, 02:26
7 A train travels from city A to city B. The average speed of the train 2 03 Nov 2014, 23:03
5 A car travels from city a to city B, a distance of 240kms. T 8 08 Aug 2014, 22:30
Display posts from previous: Sort by