# Problems on Trains

1. A train 800 m long is running at a speed of 78 km/hr. If it crosses a bridge in 1 minute, then the length of the bridge is:

A. 540 m

B. 130 m

C. 500 m

D. 260 m

Explanation:

Given, Length of the train = 800 m,
Speed of the train = 78 km/hr (convert km/hr to m/sec) = 78 * (5/18) m /sec = 21.667 m /sec
=> Speed of the train = 21.667 m /sec.
Time taken by the train to cross the bridge = 1 min = 60 sec.
Time taken by train to cross bridge = (Length of bridge + Length of train) / speed of the train
=> 60 = (Length of bridge + 800) / 21.667
=> 60 * 21.667 = Length of bridge + 800
=> 1300 = Length of bridge + 800
=> 1300 – 800 = Length of bridge
=> Length of bridge = 500 m

2. A train 360 m long is running at the speed of 45 km/hr. The time taken by it to pass a bridge 140 m long is:

A. 48 seconds

B. 42 seconds

C. 40 seconds

D. 45 seconds

Explanation:

Given, Length of train =360 m
Length of bridge =140 m
Speed of train = 45 km/hr
=> Converting into meter/ second
= 45 * (5/18) m / sec
= 12.5 m/sec
=> Speed of train = 12.5 m/sec
Required Time = (Length of train +Length of bridge) / Speed of train
= (360 + 140) / 12.5
= 500 / 12.5
= 40 sec
=> Required Time = 40 secs

3. How much time does a train 110 metres long running at the speed of 72 km/hr take to cross a bridge 132 metres in length?

A. 14.3 seconds

B. 12.1 seconds

C. 9.8 seconds

D. 12.42 seconds

Explanation:

Given, Length of train = 110 metres
Speed of passenger train =72 km/hr
=> Converting Speed from km/hr into m/sec
=> Speed of passenger train = 72 * (5/18) m/sec
= 4 * 5
= 20 m/sec
Length of bridge =132 metres

Time taken by the train to cross the bridge = (Length of the passenger train + Length of the bridge) / Speed of train
= (110 + 132) / 20
= 242 / 20
= 12.1 secs

Time taken by the train to cross the bridge = 12.1 seconds

4. A passenger train 280 m long, running with a speed of 63 km/hr will pass a pole in:

A. 15 seconds

B. 20 seconds

C. 18 seconds

D. 16 seconds

Explanation:

Given, Length of the passenger train = 280 m
Speed of the passenger train = 63 km / hr
=> To convert km/hr to m/sec multiply speed with (5 / 18)
= 63 x (5 / 18) m/sec
= 17.5 m/sec

Time taken by the train to cross a pole = Length of the passenger train / Speed of the passenger train
= 280/17.5
= 16 secs

5. In what time will a train 100 metres long cross a pole, if its speed is 144 km/hr?

A. 25 seconds

B. 5 seconds

C. 12.5 seconds

D. 2.5 seconds