Speed, Time and Distance
 A train is moving at a speed of 80 km/h and covers a certain distance in 4.5 hours. The speed of the train to cover the same distance in 4 hours is

 100 km/h
 70 km/h
 85 km/h
 90 km/h

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Distance = Speed × Time
= 80 × 4.5 = 360 km∴ Required speed = 360 = 90 kmph. 4 Correct Option: D
Distance = Speed × Time
= 80 × 4.5 = 360 km∴ Required speed = 360 = 90 kmph. 4
 Two trains are running 40 km/hr and 20 km/hr respectively in the same direction. The fast train completely passes a man sitting in the slow train in 5 seconds. The length of the fast train is


23 2 m 9  27 m

27 7 m 9  23 m


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Relative speed = 40 – 20 = 20 km/hour
= 20 × 5 m/sec. 18 ∴ Length of the faster train = 20 × 5 × 5 metres 18 = 250 = 27 7 metres 9 9 Correct Option: C
Relative speed = 40 – 20 = 20 km/hour
= 20 × 5 m/sec. 18 ∴ Length of the faster train = 20 × 5 × 5 metres 18 = 250 = 27 7 metres 9 9
 A policeman goes after a thief who has 100 metres start, if the policeman runs a kilometre in 8 min, and the thief a km in 10 min, the distance covered by thief before he is overpowered is

 350 m
 400 m
 320 m
 420 m

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Relative speed = 1000 − 1000 8 10 = 5000 − 4000 = 1000 m/minute 40 40 ∴ Required time = 100 1000 40 = 4000 = 4 m/minute 1000 ∴ Distance covered by the thief = 1000 × 4 10
= 400 metresCorrect Option: B
Relative speed = 1000 − 1000 8 10 = 5000 − 4000 = 1000 m/minute 40 40 ∴ Required time = 100 1000 40 = 4000 = 4 m/minute 1000 ∴ Distance covered by the thief = 1000 × 4 10
= 400 metres
 A boy started from his house by bicycle at 10 a.m. at a speed of 12 km per hour. His elder brother started after 1 hr 15 mins by scooter along the same path and caught him at 1.30 p.m. The speed of the scooter will be (in km/hr)

 4.5
 36

18 2 3  9

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Let the speed of Scooter be x Distance covered by cycling in
3 1 hours = Distance covered by scooter in 2 2 1 hours 4 ⇒ 12 × 7 = x × 9 2 4 ⇒ x = 12 × 7 × 2 9 = 56 = 18 2 kmph 3 3 Correct Option: C
Let the speed of Scooter be x Distance covered by cycling in
3 1 hours = Distance covered by scooter in 2 2 1 hours 4 ⇒ 12 × 7 = x × 9 2 4 ⇒ x = 12 × 7 × 2 9 = 56 = 18 2 kmph 3 3
 Two trains start from a certain place on two parallel tracks in the same direction. The speed of the trains are 45 km/hr and 40 km/hr respectively. The distance between the two trains after 45 minutes will be

 2 km 500 m
 2 km 750 m
 3 km 750 m
 3 km 250 m

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Relative speed = 45– 40 = 5 kmph
∴ Required distance = 5 × 45 km 60 = 15 km = 3 km 750 4 Correct Option: C
Relative speed = 45– 40 = 5 kmph
∴ Required distance = 5 × 45 km 60 = 15 km = 3 km 750 4