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# If a passenger sitting near the window in a train moving at 40 kmh not

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Manager
Joined: 15 Jan 2011
Posts: 108
If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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13 Jul 2011, 10:38
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71% (01:32) correct 29% (02:55) wrong based on 89 sessions

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If a passenger sitting near the window in a train moving at 40 kmh noticed that it took 3 seconds for the oncoming train to pass by, what was the speed of the oncoming train if the length of the oncoming train was 75 meters?

A. 50 kmh
B. 52 kmh
C. 56 kmh
D. 60 kmh
E. 70 kmh

M11-03
[Reveal] Spoiler: OA

Last edited by Bunuel on 12 Feb 2018, 22:17, edited 2 times in total.
Renamed the topic and edited the question.
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Joined: 26 May 2005
Posts: 551
Re: If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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13 Jul 2011, 10:45
Galiya wrote:
Hi all!
could you help me please with such kind of problem

A passenger sitting near the window in a train moving at 40 km/h, noticed that it took 3 sec. for the oncoming train to pass by. What was the speed of the oncoming train if the length of the oncoming train was 75 metres?

a)50km/h
b)52km/h
c)56km/h
d)60km/h
e)70km/h

Ru sure its C?
im getting A

3 secs to pass a 75 mts train , therefore speed = 25 meters/sec

to convert m/s to km/hrs multiply by 3.6
25*3.6 = 90
so its 90-40 = 50 .
Manager
Joined: 15 Jan 2011
Posts: 108
Re: If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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13 Jul 2011, 10:53
i dont know the answer...thats why i cannot be sure))).but in an answers list its C
Manager
Joined: 14 Apr 2011
Posts: 192
Re: If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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14 Jul 2011, 04:30
This is not a DS question, please move this to PS forum.

The answer should be a 50km/hr.

Train 1 speed=40km/h = 40*5/18 m/s
Train 2 speed = v m/s

Distance travelled = (speed1 + speed2) * time [The speeds need to be added as the trains are coming towards each other]

=> 75 = (100/9+v) * 3
=> v = 125/9 m/s = 125/9*18/5 km/h = 50km/h
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Re: If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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05 Feb 2018, 09:52
galiya wrote:
A passenger sitting near the window in a train moving at 40 km/h, noticed that it took 3 sec. for the oncoming train to pass by. What was the speed of the oncoming train if the length of the oncoming train was 75 metres?

a)50km/h
b)52km/h
c)56km/h
d)60km/h
e)70km/h

let x is speed of the oncoming train
sum of speed of both the trains * time taken=length that both the trains covered
(40+x)3/(3600)=75/1000+40*3/(3600)
after solving :
x=90 km/h
I don't know where I went wrong.

Plz someone tell where I went wrong and share the solution.
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Joined: 07 Dec 2014
Posts: 907
Re: If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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05 Feb 2018, 14:02
galiya wrote:
A passenger sitting near the window in a train moving at 40 km/h, noticed that it took 3 sec. for the oncoming train to pass by. What was the speed of the oncoming train if the length of the oncoming train was 75 metres?

a)50km/h
b)52km/h
c)56km/h
d)60km/h
e)70km/h

let s=speed of oncoming train
40+s km/h *1/1200 hrs=.075 km
s=50 km/h
a
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Re: If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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06 Feb 2018, 00:51
gracie wrote:
galiya wrote:
A passenger sitting near the window in a train moving at 40 km/h, noticed that it took 3 sec. for the oncoming train to pass by. What was the speed of the oncoming train if the length of the oncoming train was 75 metres?

a)50km/h
b)52km/h
c)56km/h
d)60km/h
e)70km/h

let s=speed of oncoming train
40+s km/h *1/1200 hrs=.075 km
s=50 km/h
a

Don't we have to consider the distance that the train travelled within those 3 s?
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Re: If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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12 Feb 2018, 02:22
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Re: If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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12 Feb 2018, 02:40
Anjalika123 wrote:
galiya wrote:
A passenger sitting near the window in a train moving at 40 km/h, noticed that it took 3 sec. for the oncoming train to pass by. What was the speed of the oncoming train if the length of the oncoming train was 75 metres?

a)50km/h
b)52km/h
c)56km/h
d)60km/h
e)70km/h

let x is speed of the oncoming train
sum of speed of both the trains * time taken=length that both the trains covered
(40+x)3/(3600)=75/1000+40*3/(3600)
after solving :
x=90 km/h
I don't know where I went wrong.

Plz someone tell where I went wrong and share the solution.

You should be considering the length of the train that is passing as the point of reference is you. Hence distance covered is 75 meters only.. Not the length of the train in which you are sitting

Posted from my mobile device
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Joined: 26 Feb 2016
Posts: 2094
Location: India
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Re: If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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12 Feb 2018, 03:18
pudipeddi wrote:
Anjalika123 wrote:
galiya wrote:
A passenger sitting near the window in a train moving at 40 km/h, noticed that it took 3 sec. for the oncoming train to pass by. What was the speed of the oncoming train if the length of the oncoming train was 75 metres?

a)50km/h
b)52km/h
c)56km/h
d)60km/h
e)70km/h

let x is speed of the oncoming train
sum of speed of both the trains * time taken=length that both the trains covered
(40+x)3/(3600)=75/1000+40*3/(3600)
after solving :
x=90 km/h
I don't know where I went wrong.

Plz someone tell where I went wrong and share the solution.

You should be considering the length of the train that is passing as the point of reference is you. Hence distance covered is 75 meters only.. Not the length of the train in which you are sitting

Posted from my mobile device

pudipeddi

The distance travelled by the train in which the passenger sat will also be taken into
consideration because the train is not stationary but moving at a speed of 40kmph
So, the train will also travel some distance in those 3 seconds.

If the incoming train travels at a speed of 40 km/hr, it would translate into $$\frac{100}{9}$$ m/s.

In 3 seconds, the train would have travelled $$\frac{100}{3}$$ meters.

The total distance travelled in 3 seconds would be $$75 - \frac{100}{3} = \frac{125}{3}$$ meters in 3 seconds.

The distance(125/9 m/s) translated in km/hr is $$\frac{125}{9}*\frac{18}{5}= 50$$kmph

Sasindran, I believe the OA has to be corrected to 50(Option A)
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Location: India
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Re: If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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12 Feb 2018, 03:43
pushpitkc wrote:

Sasindran, I believe the OA has to be corrected to 50(Option A)

Yeah pushpitkc. Please change it if you can

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Re: If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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12 Feb 2018, 07:59
galiya wrote:
A passenger sitting near the window in a train moving at 40 km/h, noticed that it took 3 sec. for the oncoming train to pass by. What was the speed of the oncoming train if the length of the oncoming train was 75 metres?

a)50km/h
b)52km/h
c)56km/h
d)60km/h
e)70km/h

Unit based question it is

Total time 3 Sec= 3/3600 Hrs= 1/1200 Hrs

Total Distance= 75 meters= 75/1000 Kms=3/40 Kms

Relative velocity will be added trains moving in same direction speed of train 1=40 km/h
train 2 lest assume S2 Total Speed= 40+S2= 3/40*1200/1=90
Hence S2=50 Km/h
A
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Re: If a passenger sitting near the window in a train moving at 40 kmh not [#permalink]

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12 Feb 2018, 22:18
Expert's post
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galiya wrote:
If a passenger sitting near the window in a train moving at 40 kmh noticed that it took 3 seconds for the oncoming train to pass by, what was the speed of the oncoming train if the length of the oncoming train was 75 meters?

A. 50 kmh
B. 52 kmh
C. 56 kmh
D. 60 kmh
E. 70 kmh

M11-03

Denote the speed of the oncoming train as $$V$$. Then its speed relative to the passenger is $$V + 40$$. 75 meters in 3 seconds is the same as 25 meters in 1 second or 90 kmh. Thus, $$V + 40 = 90$$ and $$V = 50$$ kmh.

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Re: If a passenger sitting near the window in a train moving at 40 kmh not   [#permalink] 12 Feb 2018, 22:18
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