Latest Infosys Aptitude Question SOLUTION: A train leaves Meerut at 5 a.m. and reaches Delhi at 9 a.m. Another train leaves Delhi at 7 a.m. and reaches Meerut at 10.30 a.m. At what time do the two trains travel in order to

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A train leaves Meerut at 5 a.m. and reaches Delhi at 9 a.m. Another train leaves Delhi at 7 a.m. and reaches Meerut at 10.30 a.m. At what time do the two trains travel in order to cross each other ?

Asked In Infosys divyasree (6 years ago)

Unsolved Read Solution (7)

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Read Solution (7) :

Rupak  (6 years ago)

First train takes 4 hours and the second train takes 3.5 hours.

Time ratio is 8:7. Therefore, the speed ratio will be 7:8.

Let the speeds be 7x and 8x, and distance be 28x ( 4x7 or 3.5x8).

At 7 AM, the first train must have covered a distance of 14x. Therefore, at 7 A.M. the distance between the two trains is 28x-14x=14x.

Time taken to meet = 14x/(7x+8x)=14/15 hour or 56 minutes.

Hence, the two trains meet at 7.56 AM.

Is this solution Helpfull? Yes (21) | No (5)  

  (6 years ago)

The first train started at 5.am whereas the second train started at 7 a.m
meanwhile, the first train already complete 2 hours journey

time ratios of first&second trains=t1/t2= 4/3.5=4/(7/2)=8/7
speed ratio's will become=7/8
total distance need to be cover by first train d1=s1*t1=7X*4=28X
total distance need to be cover by second train d2=s2*t2=8X*3.5=24.5X
so, let's calculate how much distance completed by the first before the second train started
distance covered in two hours by the first train =s*t=7X*2=14x
so 14X is already completed remaining distance need to cover is 28X-14X=14X
Time taken by the trains to meet = Distance between them/relative speed=14X/(7+8)X hours=14/15hr=(14/15)*60 minutes=56 minutes
At 7 AM, It takes 56 minutes to meet , At 7.56 A.M they both met.

Is this solution Helpfull? Yes (10) | No (1)  

Balamurugan  (6 years ago)

Let the total distance be x
So the speed of 1st train is x/4 and 2nd train x/3.5
In 2 hours 1st train covers half of the total distance . So remaining is only half of the
total distance(ie x/2). Let t be the time taken
t × x 4+ t × x 3.5= x 2
t = 1415
i.e. 56 min
i.e. Total time taken= 2 hrs + 56 min
Time they cross each other is 7:56 am (5+2.56) Answer 7:56 am

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Sampad Mukherjee  (6 years ago)

As train departed from Meerut at 5 A.M. and takes 4 hours to reach Delhi, so we can easily say that it should have covered half of the distance in 2 hours i.e till 7 A.M.

A train leaves Meerut at 5 am and reaches Delhi at 9 am.
Hence total time taken : 4 hours. t1 = 4 hours

A train leaves Delhi at 7 am and reaches Meerut at 10 :30 am
Hence total time taken 3.5 hours or can be written as 3 ^1/2 or t2 = 3.5 hours

Ratio of time t1 and t2 :

t1/t2 = 4/(3^1/2) or 4/(7/2) or 8/7

and the velocities be v1 and v2 and hence the ratios would be v1/v2 = 7/8

as, s= vt where s = displacement, v=velocity and t=time.

There is a time difference of 2 hours, the train leaves from the respective stations.

Time of meeting = (7/(7+8)) * 2;
or, 7/15*2 = 14/15 hours or, 14/15*60minutes = 56 minutes.

Hence, time of meeting will be 7 : 56 am.

Is this solution Helpfull? Yes (3) | No   

Sampad Mukherjee  (6 years ago)

A train leaves Meerut at 5 am and reaches Delhi at 9 am.
Hence total time taken : 4 hours. t1 = 4 hours

A train leaves Delhi at 7 am and reaches Meerut at 10 :30 am
Hence total time taken 3.5 hours or can be written as 3 ^1/2 or t2 = 3.5 hours

Ratio of time t1 and t2 :

t1/t2 = 4/(3^1/2) or 4/(7/2) or 8/7

and the velocities be v1 and v2 and hence the ratios would be v1/v2 = 7/8

as, s= vt where s = displacement, v=velocity and t=time.

There is a time difference of 2 hours, the train leaves from the respective stations.

Time of meeting = (7/(7+8)) * 2;
or, 7/15*2 = 14/15 hours or, 14/15*60minutes = 56 minutes.

Hence, time of meeting will be 5 : 56 am.

Is this solution Helpfull? Yes (2) | No (10)  

Mohit sehwal  (5 years ago)

first train is start at 5 am, it takes 4h to complete their journey and second is at 7 am, it takes 4h to complete their journey.
Let the total distance covered by train is 28km (we get the LCM of time taken both trains first is 4 and second is 7/2 we only take nominator only).
then the speed of first train is 7km/h (28/4) and the speed of first train is 8km/h (28/7*2).
first train covered distance when second train is started is 7*2= 14. ( second train is start after 2h)
then remaining distance is 28-14 = 14km.
then they cross each other at 14/15*60 = 56 minutes (15 = speed of first train +speed of second train).

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  (5 years ago)

Time taken by train M from Meerut to Delhi = 4 hours

It travels for 2 hours before train D starts.

Time taken by train D from Delhi to Meerut = 3.5 hours

Let distance between Delhi & Meerut = LCM(4,3.5) = 28 kms

Speed of Train M = 28/4 = 7 kmph

Speed of Train D = 28/3.5 = 8 kmph

Train M covers 7 x 2 = 14 km by the time Train D starts at 7 AM.

So, distance between the two trains at 7 AM is 28 - 14 = 14km

Relative speed = 7 + 8 = 15 kmph

Time taken to cross each other = 14/15 hours or 56 minutes.

=> They meet at 7:56 AM.

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