Speed, Time and Distance
- A constable is 114 metres behind a thief. The constable runs 21 metres and the thief runs 15
metres in a minute. In what time will the constable catch the thief ?
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The gap of 114 metre will be filled at relative speed.
Required time = 
114 
minutes 21 − 15 = 114 = 19 minutes 6 Correct Option: A
The gap of 114 metre will be filled at relative speed.
Required time = 114 minutes 21 − 15 = 114 = 19 minutes 6
- How much time does a train, 50 m long, moving at 68 km/ hour take to pass another train, 75 m long, moving at 50 km/hour in the same direction ?
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Both trains are moving in the same direction.
∴ Their relative speed
= (68 – 50) kmph = 18 kmph= 18 × 5 = 5 m/sec 8
Total length = 50 + 75 = 125 m∴ Required time = Total length Relative speed = 125 = 25 seconds. 5 Correct Option: D
Both trains are moving in the same direction.
∴ Their relative speed
= (68 – 50) kmph = 18 kmph= 18 × 5 = 5 m/sec 8
Total length = 50 + 75 = 125 m∴ Required time = Total length Relative speed = 125 = 25 seconds. 5
- A constable follows a thief who is 200 m ahead of the constable. If the constable and the thief run at speed of 8 km/hour and 7 km/hour respectively, the constable would catch the thief in
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The constable and thief are running in the same direction
∴ Their relative speed = 8 – 7 = 1km.= 1 × 5 m/sec. 18 ∴
Required time =200 5 18 = 200 × 18 = 720 sec 5 = 720 minutes = 12 minutes 60 Correct Option: B
The constable and thief are running in the same direction
∴ Their relative speed = 8 – 7 = 1km.= 1 × 5 m/sec. 18 ∴
Required time =200 5 18 = 200 × 18 = 720 sec 5 = 720 minutes = 12 minutes 60
- Two trains are running with speed 30 km/hr and 58 km/hr in the same direction. A man in
the slower train passes the faster train in 18 seconds. The length (in metres) of the faster train is :
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Relative speed = (58 – 30) km/hr
= 28 × 5 m/sec. 18 = 70 m/sec. 9 ∴ Length of train = 70 × 18 9
= 140 metresCorrect Option: D
Relative speed = (58 – 30) km/hr
= 28 × 5 m/sec. 18 = 70 m/sec. 9 ∴ Length of train = 70 × 18 9
= 140 metres
- Two trains travel in the same direction at the speed of 56 km/h and 29 km/h respectively. The faster train passes a man in the slower train in 10 seconds. The length of the faster train (in metres) is
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Relative speed = 56 – 29 = 27 kmph
= 27 × 5 = 15 m/sec 18 2
∴ Distance covered in 10 seconds= 15 × 10 = 75 m 2
Hence, length of train = 75 m.Correct Option: C
Relative speed = 56 – 29 = 27 kmph
= 27 × 5 = 15 m/sec 18 2
∴ Distance covered in 10 seconds= 15 × 10 = 75 m 2
Hence, length of train = 75 m.
