Time & Distance (2)

1. Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively . If they cross each other in 23 seconds, what is the ratio of their speeds?
1. Insufficient data
2. 3 : 1
3. 1 : 3
4. 3 : 2

Answer & Explanation

Answer:- 4

Explanation :-

Let the speeds of First trains be x m/sec and That of Second train be  y m/sec
distance = speed * time] Then,
Length of the first train = 27x metres,
Length of the second train = 17y metres.
(27x +17y)/(x + y) = 23
27x + 17y = 23x +23y
4x = 6y
x/y = 3/2

 

2. A jogger is running at 9 kmph alongside a railway track in 240 meters ahead of the engine of a 120 meters long train . The train is running at 45 kmph in the same direction. how much time does it take for the train to pass the jogger?
1. 46
2. 36
3. 18
4. 22

Answer & Explanation

Answer:- 2

Explanation :-

Relative Speed = (45-9) = 36 kmph = 36*(5/18) = 10 m/sec
Distance to cover = 240 + 120 = 360 metres
Time = Distance/Speed
Time = 360/10 = 36 sec

 

3. Two trains of equal length are running on parallel lines in the same direction at 46 km/hr and 36 km/hr. If the faster train passes the slower train in 36 seconds,what is the length of each train?
1. 88
2. 70
3. 62
4. 50

Answer & Explanation

Answer:- 4

Explanation :-

Lets suppose  the length of each train is x meter
Therefore , Distance = x+x = 2x
Relative Speed = 46-36 = 10 km/hr = 10*(5/18) = 25/9 m/sec
Distance = Speed*Time
2x = (25/9) * 36
2x = 100 => x = 50
Therefore , Length of each train = 50 metres

 

4. Two trains having length of 140 m and 160 m long run at the speed of 60 km/hr and 40 km/hr respectively in opposite directions (on parallel tracks). The time which they take to cross each other, is
1. 10.8 s
2. 12 s
3. 9.8 s
4. 8 s

Answer & Explanation

Answer:- 1

Explanation :-

Relative speed = (60 + 40) km/hr =[ 100 x ( 5 / 18 ) ] m/sec = ( 250 /9 ) m/sec.
Distance covered = (140 + 160) m = 300 m.
Time = [ 300 x ( 9/250 ) ] sec = ( 54/ 5 ) sec = 10.8 sec.

 

5. Two trains are moving in opposite directions with speed of 60 km/hr and 90 km/hr respectively. Their lengths are 1.10 km and 0.9 km respectively. the slower train cross the faster train in — seconds
1. 56
2. 48
3. 47
4. 26

Answer & Explanation

Answer:- 2

Explanation :-

Relative Speed = 60 + 90 = 150 km/h = 150 (5/18) m/s = 125/3 m/s
Distance covered = (1.10 + 0.9) km = 2 km = 2000 metres
Time =  distance/speed
The slower train cross the faster train in = 2000 /(125/3) = 2000 * 3/125 = 48 sec

 

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