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Senior Manager  Joined: 17 Aug 2005
Posts: 297
Location: Boston, MA
A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at  [#permalink]

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32 00:00

Difficulty:   45% (medium)

Question Stats: 69% (02:33) correct 31% (02:51) wrong based on 486 sessions

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A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at 12 noon. Ten minutes later, a train leaves Tokyo for Kyoto traveling 160 miles per hour. If Tokyo and Kyoto are 300 miles apart, at what time will the trains pass each other?

A. 12:40pm
B. 12:49pm
C. 12:55pm
D. 1:00pm
E. 1:05pm

Originally posted by buckkitty on 05 Jun 2006, 11:54.
Last edited by Bunuel on 11 May 2015, 02:51, edited 1 time in total.
Renamed the topic, edited the question and added the OA.
Senior Manager  Joined: 17 Aug 2005
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Location: Boston, MA
Re: A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at  [#permalink]

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9
Train A: going from K to T
Train B: going from T to K

First I calculated how far Train A will have travelled by the time Train B starts at 12:10:
10 minutes at 240 mph
1/6*240=40miles

They have 300-40=260 miles to travel to meet each other.

I found the combined rate of the two trains
Rate(A) + Rate(B) = 400mph

Divide Distance/Rate to find total time each will travel:
260/400=39/60 >>> 39 Minutes to meet

12:10+39 minutes = 12:49 or Answer B
##### General Discussion
Manager  Joined: 10 May 2006
Posts: 135
Location: USA
Re: A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at  [#permalink]

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1
1
buckkitty wrote:
A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at 12 noon. Ten minutes later, a train leaves Tokyo for Kyoto traveling 160 miles per hour. If Tokyo and Kyoto are 300 miles apart, at what time wil the trains pass each other?

A. 12:40pm
B. 12:49pm
C. 12:55pm
D. 1:00pm
E. 1:05pm

I would love to know the approach you guys take to solving this. I approached it a little differently from the book. The source is MGMAT word problem translations book.

B -

The bullet train will have travelled 240 x (10/60) miles after the first 10 minutes = 40 miles.

At 12:10 , the bullet train and the train are 260 miles apart (=300-40). To calculate when they will pass:

260 = 240*(60)*x + 160*(60)*x where x = the time it takes for them to reach one another in minutes

x = 39 minutes for the trains to pass each other AFTER 12:10.

Therefore the trains must have passed each other at 12:49
Director  Joined: 16 Aug 2005
Posts: 669
Location: France
Re: A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at  [#permalink]

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2
Let distance travelled by A be x miles
Speed A = 240/60 = 4 miles per minue
Speed B = 160/60 = 8/3 miles/min
time = distance/speed
Distance travelled by A in 10 minutes = 40 miles.

Distance remaining = 260 miles.

3x/8 = (260-x)/4
12x = 260.8 - 8x
x = 26.4 = 104

time = 39mins

Hence B
Director  Joined: 30 Jun 2008
Posts: 800
A bullet train leaves Kyoto for Tokyo traveling 240 miles  [#permalink]

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A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at 12 noon. Ten minutes later, a train leaves Tokyo for Kyoto traveling 160 miles per hour. If Tokyo and Kyoto are 300 miles apart, at what time wil the trains pass each other?

A. 12:40pm
B. 12:49pm
C. 12:55pm
D. 1:00pm
E. 1:05pm
Manager  Joined: 28 Apr 2008
Posts: 96
Re: MGMAT - RATE PROBLEM  [#permalink]

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4
1
B

in 10 minutes tha train travels 40 miles- the rest is 260.

x=v*t

=> 260= (160+240)*t

=> t=39 minutes

39+10=49

Director  Joined: 23 May 2008
Posts: 522
Re: MGMAT - RATE PROBLEM  [#permalink]

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1
rino wrote:
B

in 10 minutes tha train travels 40 miles- the rest is 260.

x=v*t

=> 260= (160+240)*t

=> t=39 minutes

39+10=49

thats an interesting , shorter approach, I got the same answer but im sure it took me longer

R=T*D

240t=d
160(t-1/6)=300-d

160t-160=300-240t

t=49/60
Director  Joined: 30 Jun 2008
Posts: 800
Re: MGMAT - RATE PROBLEM  [#permalink]

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amitdgr wrote:
A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at 12 noon. Ten minutes later, a train leaves Tokyo for Kyoto traveling 160 miles per hour. If Tokyo and Kyoto are 300 miles apart, at what time will the trains pass each other?

A. 12:40pm
B. 12:49pm
C. 12:55pm
D. 1:00pm
E. 1:05pm

!)Train K starts from Kyoto at 12:00 noon. It moves at the speed of 240 mph. Say it covers 300-x miles

2)Train T starts from Tokyo at 12:10 PM at a speed of 160 mph. Say it covers the rest of x miles

From (1) we have 300-x = 240(t+1/6) [ we have "+1/6" here since Train K travels 10 minutes or 1/6 hours longer than train T]

and From (2) we have x=160t

combining above two equations:
300-160t=240t + 40
260 = 400t

t= 26/40 = 13/20 hours = (13/20)*60 = 39 mins.

12:10 + :39 = 12:49
Director  Joined: 05 Jul 2008
Posts: 893
Re: MGMAT - RATE PROBLEM  [#permalink]

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rino wrote:
amitdgr wrote:
rino wrote:
B

in 10 minutes tha train travels 40 miles- the rest is 260.

x=v*t

=> 260= (160+240)*t

=> t=39 minutes

39+10=49

That is a pretty neat method rino.

is 160+240 the relative speed between two trains ?

Quote:
yes- it's the relative speed

Good method.

I did the long method too

(t+1/6) 240 + 160 t = 300
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Posts: 165
Location: India
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14) A bullet train leaves kyoto for Tokyo traveling 240 miles per hour at 12 noon. Ten minutes later, a train leaves Tokyo for Kyoto traveling 160 miles per hour.If Tokyo and Kyoto are 300 miles apart, at what time ill the trains pass each other?

a) 12.40 pm
b) 12.49 pm
c) 12.55 pm
d) 1.00 pm
e) 1.05 pm

Catch up time= Distance between the 2/Speed of Train from K->T + Speed of Train from T->K

300/240+160 = 45 mins
as Train from T->k started 10 mins late catch up time will be 12.55
If i calculate with other method

240(t+1/6)+ 160t = 300

i got t as 39 mins

as Train from T->k started 10 mins late catch up time will be 12.49

WHEN CAN WE APPLY THE FORMULA TO CALCULATE Catch up time because in this case its not giving correct answer.
Director  Status: Impossible is not a fact. It's an opinion. It's a dare. Impossible is nothing.
Affiliations: University of Chicago Booth School of Business
Joined: 03 Feb 2011
Posts: 641

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1
300/240+160 = 45 mins ---> This is wrong
You are assuming that train K->T started the same instant that the train T->K started. So train T->K traveled 1/6 * 160 miles more and hence the "kiss" time went down by 4 mins. i.e. 45 mins. However the actual time to intersect is 49 mins.

as Train from T->k started 10 mins late catch up time will be 12.55 --->

When using the relative speed you assumed if one train were still, the other train will catch up at effectively 400 mph. So 400/6 miles is covered in 1/6 hr. This cannot be undone by simple arithmetic as adding 10 mins to the time of intersect. This doesn't work.

In fact the correct assumption is that for the first 1/6 hr (10 mins), the slower train was still and only the faster train was moving.

GMATD11 wrote:
14) A bullet train leaves kyoto for Tokyo traveling 240 miles per hour at 12 noon. Ten minutes later, a train leaves Tokyo for Kyoto traveling 160 miles per hour.If Tokyo and Kyoto are 300 miles apart, at what time ill the trains pass each other?

a) 12.40 pm
b) 12.49 pm
c) 12.55 pm
d) 1.00 pm
e) 1.05 pm

Catch up time= Distance between the 2/Speed of Train from K->T + Speed of Train from T->K

300/240+160 = 45 mins
as Train from T->k started 10 mins late catch up time will be 12.55
If i calculate with other method

240(t+1/6)+ 160t = 300

i got t as 39 mins

as Train from T->k started 10 mins late catch up time will be 12.49

WHEN CAN WE APPLY THE FORMULA TO CALCULATE Catch up time because in this case its not giving correct answer.
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1
Let the trains meet after x hours.

240x + (x - 1/6)160 = 300

24x + 16x - 16/6 = 30

40x = 16/6 + 30

=> 40x = 196/6

=> 10x = 49/6

So it wil be after 49/60 hr or 49 min, so 12:49, hence the answer is 12:49 PM
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Manager  Joined: 18 Oct 2010
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train A-------------------B
r: 240 ------------------160
t: t+10/60=t+1/6 --------t (cause A moved 10 mins ealier)
S: 300-[240*(t+1/6)-----160 t
300-240t-40=160t so t=1 hour and 5 mins

from what i learned from MGMAT this is " the kiss/ crash"

train ----rate-----time-----distance
A---------a--------t--------at= A's distance
B---------b---------t-------bt=B's distance
total-----(a+b)-----t-------total distance covered
Senior Manager  S
Status: No dream is too large, no dreamer is too small
Joined: 14 Jul 2010
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Time taken to meet = Distance/relative speed
Second train started 10 minutes later, the first train travels in 10 minutes = 240/60*10=40 miles
so they have to travel 300-40=260 miles
now, time= [260/(240+160)]*60= 39 minutes
as 10 minutes later 39+10=49 minutes

Ans. B
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240(t +1/6) +160t = 300
t = 39 mins
t+10 = 49 mins

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Re: A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at  [#permalink]

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buckkitty wrote:
A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at 12 noon. Ten minutes later, a train leaves Tokyo for Kyoto traveling 160 miles per hour. If Tokyo and Kyoto are 300 miles apart, at what time will the trains pass each other?

A. 12:40pm
B. 12:49pm
C. 12:55pm
D. 1:00pm
E. 1:05pm

This is a very beautiful question for any student of clear thinking. You could apply the right strategy/formular and blow the solution by an error in the not very short solution process.
Rate x Time = Distance
Either $$240t + 160(t - 1/6) = 300$$

OR $$240(t + 1/6) + 160t = 300$$

will give you the solution; the first gives you t = 49 and the second gives you t = 39.
The first is straight forward without a trap cos it came straight out from the wording of the question without manipulation.
You might say the second is great since you were aware that you must add $$\frac{(1}{6)}$$hours to it. Well,in a CAT, if you had got an answer choice that says 12:39pm then you might have fallen into the trap and FAILED THE QUESTION pitifully with your head held high.
I would always want to follow the question prompt like I'm not too smart.
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Joined: 02 Aug 2009
Posts: 8309
Re: A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at  [#permalink]

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Nez wrote:
buckkitty wrote:
A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at 12 noon. Ten minutes later, a train leaves Tokyo for Kyoto traveling 160 miles per hour. If Tokyo and Kyoto are 300 miles apart, at what time will the trains pass each other?

A. 12:40pm
B. 12:49pm
C. 12:55pm
D. 1:00pm
E. 1:05pm

This is a very beautiful question for any student of clear thinking. You could apply the right strategy/formular and blow the solution by an error in the not very short solution process.
Rate x Time = Distance
Either $$240t + 160(t - 1/6) = 300$$

OR $$240(t + 1/6) + 160t = 300$$

will give you the solution; the first gives you t = 49 and the second gives you t = 39.
The first is straight forward without a trap cos it came straight out from the wording of the question without manipulation.
You might say the second is great since you were aware that you must add $$\frac{(1}{6)}$$hours to it. Well,in a CAT, if you had got an answer choice that says 12:39pm then you might have fallen into the trap and FAILED THE QUESTION pitifully with your head held high.
I would always want to follow the question prompt like I'm not too smart.

Hi Nez,
You are absolutely correct that a Q like this can be blown to pieces if you take one wrong step..
If I were to do this, I will not get into making equation...
i will see how much distance is left between two when both are in motion..
1) in 10 min, train from K to T would have travelled= 240*10/60=40..
2) so distance between the two when Train starts from T to K= 300-40=260..
3) combined speed as both travelling towards each other= 240+160=400.
4) they will meet after= 260/400 * 60=39 minutes..
time after 39 minutes= 12:10+39 min=12:49..
This method too finally does what the equation does but slightly less error prone

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A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at  [#permalink]

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buckkitty wrote:
A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at 12 noon. Ten minutes later, a train leaves Tokyo for Kyoto traveling 160 miles per hour. If Tokyo and Kyoto are 300 miles apart, at what time will the trains pass each other?

A. 12:40pm
B. 12:49pm
C. 12:55pm
D. 1:00pm
E. 1:05pm

[b]AS, later train start ten minutes later , so the first train(from Kyoto to Tokyo) cover distance in ten minutes equals

(240/60*10 ) 40 miles. Rest of the distance 300-40 = 260.therefore, two train together will cover up this distance

Relative speed will be (240 + 160) 400 Miles per hour. required time = (260/400*60) 39 minutes.

Total time would be 39+10 = 49 minutes . they will pass each other at 12: 49 pm.

Kudos if it helps.Thanks
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Re: A bullet train leaves Kyoto for Tokyo traveling 240 miles per hour at  [#permalink]

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