Aptitude - Problems on Trains
Overview Exercise "Time and tide wait for none."
- Alexander Pope
17.
A train 800 metres long is running at a speed of 78 km/hr. If it crosses a tunnel in 1 minute, then the length of the tunnel (in meters) is:
Answer: E
Explanation:
Speed =
78 x
5
m/sec
=
65
m/sec.
18
3
Time = 1 minute = 60 seconds.
Let the length of the tunnel be x metres.
Then,
800 + x
=
65
60
3
x ) = 3900
x = 500.
18.
A 300 metre long train crosses a platform in 39 seconds while it crosses a signal pole in 18 seconds. What is the length of the platform?
A. 320 m B. 350 m C. 650 m D. Data inadequate
Answer: B
Explanation:
Speed =
300
m/sec =
50
m/sec.
18
3
Let the length of the platform be x metres.
Then,
x + 300=
50
39
3
x + 300) = 1950
x = 350 m.
19.
A train speeds past a pole in 15 seconds and a platform 100 m long in 25 seconds. Its length is:
A. 50 m B. 150 m C. 200 m D. Data inadequate
Answer: E
Explanation:
Let the length of the train be x metres and its speed by y m/sec.
Then,
x = 15 y =
x .
y 15
x + 100=
x
25
15
x + 100) = 25x
x + 1500 = 25x
x
x = 150 m.
20.
A train moves past a telegraph post and a bridge 264 m long in 8 seconds and 20 seconds respectively. What is the speed of the train?
A. 69.5 km/hr B. 70 km/hr C. 79 km/hr D. 79.2 km/hr
Answer: D
Explanation:
Let the length of the train be x metres and its speed by y m/sec.
Then,
x = 8 x = 8y
y
y + 264 = 20y
y = 22.
22 x
18
km/hr = 79.2 km/hr.
5
miles long. The train is 
mile long. How long does it take for the train to pass through the tunnel from the moment the front enters to the moment the rear emerges?
Time taken
3(800 + x) = 3900