Problems on Trains Questions

FACTS  AND  FORMULAE  FOR  PROBLEMS  ON  TRAINS

 

 

1. a km/hr = [a x (5/18)] m/s.

 

2. a m/s = [a x (18/5)] km/hr.

 

3. Time taken by a train of length l metres to pass a pole or a standing man or a signal post is equal to the time taken by the train to cover l metres.

 

4. Time taken by a train of length 1 metres to pass a stationary object of length b metres is the time taken by the train to cover (1 + b) metres.

 

5. Suppose two trains or two bodies are moving in the same direction at u m/s and v m/s, where u > v, then their relatives speed = (u - v) m/s.

 

6. Suppose two trains or two bodies are moving in opposite directions at u m/s and v m/s, then their relative speed = (u + v) m/s.

 

7. If two trains of length a metres and b metres are moving in opposite directions at u m/s and v m/s, then time taken by the trains to cross each other = (a+b)(u+v)sec.

 

8. If two trains of length a metres and b metres are moving in the same direction at u m/s and v m/s, then the time taken by the faster train to cross the slower train = a+bu-vsec.

 

9. If two trains (or bodies) start at the same time from points A and B towards each other and after crossing they take a and b sec in reaching B and A respectively, then (A's speed) : (B’s speed) = b:a

Q:

A jogger running at 9 kmph alongside a railway track is 240 metres ahead of the engine of a 120 metre long train running at 45 kmph in the same direction. In how much time will the train pass the jogger  ?

A) 10 sec B) 48 sec
C) 36 sec D) 56 sec
 
Answer & Explanation Answer: C) 36 sec

Explanation:

Given speed of jogger = 9 kmph
Speed of train = 45 kmph
As they are in same direction,
Relative speed = 45 - 9 = 36 kmph = 36x5/18 = 10 m/s
Distance = 240 + 120 = 360 mts
Time = distance/speed = 360/10 = 36 sec.

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2 4673
Q:

A passenger train covers the distance between station K and L, 40 minutes faster than a goods train. Find this distance between K and L if the average speed of the passenger train is 50 km/h and that of goods train is 30 km/h?

A) 50 kms B) 48 kms
C) 46 kms D) 44 kms
 
Answer & Explanation Answer: A) 50 kms

Explanation:

Let the distance be 'd' kms.

According to the given data,

d30 - d50 = 4060 hrs=> 6d = 300=> d = 50 kms.

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16 4621
Q:

A train travelling at 48 kmph crosses another train, having half its length and travelling in opposite direction at 42 kmph, in 12 sec. It also covers a bridge in 45 sec. Find the length of the bridge ?

A) 250 mts B) 400 mts
C) 320 mts D) 390 mts
 
Answer & Explanation Answer: B) 400 mts

Explanation:

Let the length of the 1st train = L mts

Speed of 1st train = 48 kmph

Now the length of the 2nd train = L/2 mts

Speed of 2nd train = 42 kmph

Let the length of the bridge = D mts

Distance = L + L/2 = 3L/2

Relative speed = 48 + 42 = 90 kmph = 90 x 5/18 = 25 m/s(opposite)

Time = 12 sec

=> 3L/2x25 = 12

=> L = 200 mts

Now it covers the bridge in 45 sec

=> distance = D + 200

Time = 45 sec

Speed = 48 x5/18 = 40/3 m/s

=> D + 200/(40/3) = 45

=> D = 600 - 200 = 400 mts

Hence, the length of the bridge = 400 mts.

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15 4619
Q:

The length of two superfast trains are 140 mts and 160 mts respectively. If they run at the speed of 60 km/hr and 80 km/hr respectively in opposite direction, find the time in which they will cross each other ? 

A) 7.71 sec B) 10.48 sec
C) 9.36 sec D) 8.45 sec
 
Answer & Explanation Answer: A) 7.71 sec

Explanation:

Given L1 = 140 m

L2 = 160 m

S1 = 60 km/hr

S2 = 80 km/hr

From the question we get,

S1 + S2 = (L1 + L2) / T

=> (60 + 80) 5/18 m/s = 140 + 160/T

=> T = 54/7 = 7.71 sec

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8 4390
Q:

Train K crosses a pole in 30 seconds and train L crosses the same pole in one minute and 20 seconds. The length of train K is three-fourths the length of train L. What is the ratio of the speed of train K to that of train L   ?

A) 1 : 3 B) 2 : 1
C) 3 : 1 D) 1 : 2
 
Answer & Explanation Answer: B) 2 : 1

Explanation:

Given that train K crosses a pole in 30 seconds and train L crosses the same pole in one minute and 15 seconds.

Let the length of train K be Lk and that of train L be Ll

given that Lk = 3/4 Ll

As the train K and L crosses the pole in 30 seconds and 80 seconds respectively,
=> Speed of train K = sk = Lk/30

Speed of train L = sl = Ll/80

Lk = 3/4 Ll
=> sk = 3/4 Ll/(30) = Ll/40

Ratio of their speeds = sk : sl
= Ll/40 : Ll/80

=> 1/40 : 1/80  =  2 : 1

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7 3829
Q:

A 150 m long train crosses another 210 m long train running in the opposite direction in 10.8 seconds. If the shorter train crosses a pole in 12 seconds, what is the speed of longer train ?

A) 75 kmph B) 80 kmph
C) 54 kmph D) 45 kmph
 
Answer & Explanation Answer: A) 75 kmph

Explanation:

Total distance = 150 + 210 = 360 mts

Time taken to cross each other when moving in opposite direction = 10.8 sec

Relative speed of trains = (350/10.8) x 18/5 = 3600/30 = 120 kmph

Speed of shorter train = (150/12) x 18/5 = 45 kmph

 

Hence, speed of longer train = 120 - 45 = 75 kmph.

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6 3205
Q:

A train takes 10 sec to cross a bridge of length 100 m travelling at 90 kmph. Find the length of the train in meters.

A) 130 B) 120
C) 140 D) 150
 
Answer & Explanation Answer: D) 150

Explanation:
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12 2826
Q:

A train 150 m long is running with a speed of 68 km/h. In what time will it pass a man who is running at 8 km/ h in the same direction in which the train is going?

A) 8 sec B) 8.5 sec
C) 9 sec D) 9.5 sec
 
Answer & Explanation Answer: C) 9 sec

Explanation:

Relative speed = 68-8 = 60 km/hr = 60 X 5 / 18 m/s = 50/3 m/s

Total distance = 150 m

Time taken to pass a man running in same direction = 150 X 3/50 = 9 seconds

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