Aptitude - Two trains of same length, moving in opposite directions cross in 18 seconds. The speed of the 2 tra

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Two trains of same length, moving in opposite directions cross in 18 seconds. The speed of the 2 trains being 42kmph and 48kmph. What is the length of the trains in meters?

225 meters

Total Answers and Comments: 4

Last Update: December 07, 2006

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Submitted by: vkparthipan

don tconfuce this is correct one..

first train length x metre

same length so 2nd train x metre

total length 2x

first train speed in km/hr=42

conversion to me/sec 42*8/15=35/3 m/s

2nd=40/3 m/s

relative speed opposite so 75/3

totaldistance/speed=time

2x/75/3=18

6x/75=18

so x=225

Above answer was rated as good by the following members:
senthilkumar3061986, killoooo

June 04, 2006 04:25:40

Hari

RE: Two trains of same length, moving in opposite dire...

when the two trains cross themselves in 18 seconds they will be move 24meters and 21 metres by their speed.so the trains length is 22.5 meters.

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June 19, 2006 03:13:24

vkparthipan

RE: Two trains of same length, moving in opposite dire...

don tconfuce this is correct one..

first train length x metre

same length so 2nd train x metre

total length 2x

first train speed in km/hr 42

conversion to me/sec 42*8/15 35/3 m/s

2nd 40/3 m/s

relative speed opposite so 75/3

totaldistance/speed time

2x/75/3 18

6x/75 18

so x 225

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2 0

Overall Rating: +2

July 09, 2006 13:51:23

Divya Harnadh Babu Sanam

RE: Two trains of same length, moving in opposite dire...

42 kmhr 42*5/18

48 kmhr 48*5/18

therefore (42+48)*5/18 25 msec

so 18 (x+x)25

x 22.5 metres

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December 07, 2006 05:53:45

vishwa828

Member Since: December 2006 Contribution: 7

RE: Two trains of same length, moving in opposite dire...

use the formula t ((a+b)/(u+v)) where a b are the train lengths and u v are the velociities of the trains and t is the time so we get 225 m as answer here!

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