Tackling ‘train’ questions in ‘time and distance’ for Police recruitment exam
Hyderabad: This article is in continuation to the last article on preparation for the Sub-Inspector of Police recruitment exam. Here are some practice questions and solutions on the Time and Distance topic. Trains: It is a part of Time and Distance. The train-based questions depend on time, distance and speed. Before the question, first, let […]
Hyderabad: This article is in continuation to the last article on preparation for the Sub-Inspector of Police recruitment exam. Here are some practice questions and solutions on the Time and Distance topic.
Trains: It is a part of Time and Distance. The train-based questions depend on time, distance and speed. Before the question, first, let us will discuss the basics in trains.
* If a train has to cover a standing person or a tree or pole, then train has to cover its own length.
Here Distance = Length of the train
* If a train has to cross a platform or a bridge, then train has to cover the sum of lengths of train and platform or bridge.
Here Distance = Sum of lengths of train and platform or bridge
* If two trains are running in the same direction, when they cross each and other, the distance and relative speeds are as follow:
Distance = Sum of lengths of two trains
Relative Speed = Difference between speeds of two trains
So, the time taken by the trains to cross each other = Distance/Speed
* However, if two trains are running in opposite direction, when they cross each and other, the distance and relative speeds are as follow.
Distance = Sum of lengths of two trains
Relative Speed = Sum of speeds of two trains
So, the time taken by the trains to cross each other = Distance/Speed
Now, we will discuss some examples:
1. Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 23 seconds. Then, find the ratio of their speeds.
Solution:
Let the speeds of the two trains be x m/sec and y m/sec respectively.
Then, length of the first train = 27x metres
And the length of the second train = 17y metres.
(27x 17y)/(x y) =23
27x 17y = 23x 23y
4x = 6y
x/y = 3:2
2. The 200 m and 250 m lengths of two trains are running at 45 km/hr and 99 km/hr respectively. If they are running in the same direction on parallel railway tracks, then at what time will they cross each other.
Solution:
Distance = 200 250 = 450 m
Relative Speed = 99 – 45 = 54 km/hr = 54 ×5/18 = 15 m/s
Time = 450 / 15 = 30 Seconds
3. A train crosses a standing person in 12 seconds and it will cross 120 m length of platform in 16 seconds. Find the length and speed of train?
Solution:
Let length of train = x m
Distance = x m, Time = 12 seconds
The train will cover ‘x’ plus extra 120 m in 16 seconds.
Therefore, the train will cover 120 m in 16 – 12 = 4 seconds
Distance = 120 m
Time = 4 seconds
Speed = 120/4 = 30 m/s
Length of the train = 12 × 30 = 360 m
4. A train passes a station platform in 36 seconds and a man standing on the platform in 20 seconds. If the speed of the train is 54 km/hr, then what is the length of the platform?
Solution:
Speed = 54 km/hr = 54 ×5/18 = 15 m/s
Length of the train = 20 × 15 = 300 m
Let the length of the platform is ‘x’ m
Then (x 300)/36=15
x 300 = 540
x = 540 – 300 = 240 m
Therefore, the length of the platform = 240 m
5. Say, 300 m and 400 m lengths of two trains are running at 88 km/hr and 92 km/hr respectively. If they are running in opposite direction on parallel railway tracks, then at what time they cross each and other?
Solution:
Distance = 300 400 = 700 m
Relative Speed = 88 92 = 180 km/hr = 180 × 5/18 = 50 m/s
Time = 700 / 50 = 14 sec.
6. About 240 m length of train is running at 80 km/hr. Then, at what time it will cross a girl, who is running at 8 km/hr in the same direction?
Solution:
Distance = 240 m
Relative Speed = 80 – 8 = 72 km/hr = 20 m/s
Time = 240 / 20 = 12 sec
7. Say, 350 m length of train is running at 82 km/hr. Then, at what time it will cross a boy, who is running at 8 km/hr in the opposite direction?
Solution:
Distance = 350 m
Relative Speed = 82 8 = 90 km/hr = 25 m/s
Time = 350/ 25 = 14 sec
Banda Ravipal Reddy
Director, SIGMA
Sai Institute of General Mental Ability
Hyderabad
Ph. 9491614131
Now you can get handpicked stories from Telangana Today on Telegram everyday. Click the link to subscribe.
Click to follow Telangana Today Facebook page and Twitter .
