Problems on Trains

11 )

Two stations A & B are 110 km apart on a straight line. One train starts from A at 7am and travels towards B at 20 kmph. Another train starts from B at 8am an travels toward A at a speed of 25 kmph. At what time will they meet

7 am

9:30 am

10 am

10:45 am

11 am

View Solution

Answer :

Suppose the train meet x hr after 7am

Distance covered by A in x hr=20x km

20x+25(x-1) = 110

45x=135

x=3

So they meet at 10 am

12 )

A train travelling at 48kmph completely crosses another train having half its length and travelling in opposite direction at 42kmph in 12 sec. It also passes a railway platform in 45sec. the length of platform is

350m

400m

440m

445m

455m

View Solution

Answer :

Let the length of the first train be x mt

then, the length of second train is x/2 mt

relative speed = 48+42 kmph = 90 * 5/18 m/s = 25m/s

(x+ x/2) / 25 = 12

x = 200

Length of the train is 200m

Let the length of the platform be y mt

speed of the first train = 48 * 5/18 m/s = 40/3 m/s

200 + y * 3/40 = 45

y = 400m

13 )

The length of a running train in 30% more than the length of another train B running in the opposite direction. To find out the speed of train B, which of the following information given in the statements P & Q is sufficient

P : The speed of train A is 80 kmph

Q : They took 90 sec to cross each other

Either P & Q is sufficient

Both P & Q are not sufficient

only Q is sufficient

Both P & Q are need

only P is sufficient

View Solution

Answer :

Let the length of the train A be x m

Length of the train B = 130/100 x m =13x/10 m

Let the speed of B be y mph, speed of the train A=80mph

relative speed= y+80 * 5/18 m/s

time taken by the trains t cross each other is given by

90 = (x + 13x/10)/ (5y+400 / 18)

to find y, clearly x is also needed

so, both P & Q are not sufficient

14 )

The speed of a train A, 100m long is 40% more than then the speed of another train B,180m long running in opposite direction. To find out the speed of B, which of the information given in statements P & Q is sufficient

P :The two trains crossed each other in 6 seconds

Q : The difference between the speed of the trains is 26kmph

Only P is sufficient

Only Q is sufficient

Both P & Q are needed

Both P & Q are not sufficient

cant determined

View Solution

Answer :

Let speed of B be x kmph

then, speed of A =140x/100 kmph =7x/5 mph

relative speed = x + 7x/5 =2x/3 m/s

time taken to cross each other = (100+180)*3/2x s =420/x s

now, 420/x = 6

x=70 mph

thus, only P is sufficient

15 )

The train running at certain speed crosses a stationary engine in 20 seconds. To find out the speed of the train, which of the following information is necessary

Only the length of the train

only the length of the engine

Either the length of the train or length of engine

Both the length of the train or length of engine

cant be determined

View Solution

Answer :

Since the sum of lengths of the train and the engine is needed, so both the length must be known.

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