Speed, Time and Distance
 A moving train passes a platform 50 metres long in 14 seconds and a lamppost in 10 seconds. The speed of the train is

 24 km/hr.
 36 km/hr.
 40 km/hr.
 45 km/hr.

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Suppose length of train be x
According to questionx + 50 = x 14 10
⇒ 14x = 10x + 500
⇒ 4x = 500⇒ x = 500 = 125 m 4
Therefore, speed= 125 × 18 = 45 kmph 10 5 Correct Option: D
Suppose length of train be x
According to questionx + 50 = x 14 10
⇒ 14x = 10x + 500
⇒ 4x = 500⇒ x = 500 = 125 m 4
Therefore, speed= 125 × 18 = 45 kmph 10 5
 A person standing on a railway platform noticed that a train took 21 seconds to completely pass through the platform which was 84 m long and it took 9 seconds in passing him. The speed of the train was

 25.2 km/hour
 32.4 km/hour
 50.4 km/hour
 75.6 km/hour

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Let the length of train be x metres.
When the train crosses the standing man,its speed = x 9
When the train crosses the platform of length 84 m, its speed= x + 84 21 Obviously, x = x + 84 9 21
⇒ 21x – 9x = 9 × 84
⇒ 12x = 9 × 84⇒ x = 9 × 84 = 63 m 12 ∴ Required speed = 63 m/sec 9 = 63 × 18 kmph = 25.2 kmph 9 5 Correct Option: A
Let the length of train be x metres.
When the train crosses the standing man,its speed = x 9
When the train crosses the platform of length 84 m, its speed= x + 84 21 Obviously, x = x + 84 9 21
⇒ 21x – 9x = 9 × 84
⇒ 12x = 9 × 84⇒ x = 9 × 84 = 63 m 12 ∴ Required speed = 63 m/sec 9 = 63 × 18 kmph = 25.2 kmph 9 5
 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 ?

 69.5 km/hr
 70 km/hr
 79 km/hr
 79.2 km/hr

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Let the length of train be x metres.
Then, speed of train when itpasses a telegraph post = x m/sec. 8
and speed of train, when itpasses the bridge = x + 264 20
Clearly,x = x + 264 8 20 ⇒ x = x + 264 2 5
⇒ 5x = 2x + 528
⇒ 3x = 528⇒ x = 528 = 176m 3 ∴ Speed of train = 176 = 22 m/sec. 8 = 22 × 18 Kmph 5
= 79.2 kmphCorrect Option: D
Let the length of train be x metres.
Then, speed of train when itpasses a telegraph post = x m/sec. 8
and speed of train, when itpasses the bridge = x + 264 20
Clearly,x = x + 264 8 20 ⇒ x = x + 264 2 5
⇒ 5x = 2x + 528
⇒ 3x = 528⇒ x = 528 = 176m 3 ∴ Speed of train = 176 = 22 m/sec. 8 = 22 × 18 Kmph 5
= 79.2 kmph
 A train passes a man standing on a platform in 8 seconds and also crosses the platform which is 264 metres long in 20 seconds. The length of the train (in metres) is :

 188
 176
 175
 96

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Rule 10 and Rule 1,
Let length of train be x m∴ Speed of train = x + 264 20 Also, speed of train = x 8 Obviously, x = x + 264 8 20 ⇒ x = x + 264 2 5
⇒ 5x = 2x + 528
⇒ 5x – 2x = 528
⇒ x = 528 ÷ 3 = 176 mCorrect Option: B
Rule 10 and Rule 1,
Let length of train be x m∴ Speed of train = x + 264 20 Also, speed of train = x 8 Obviously, x = x + 264 8 20 ⇒ x = x + 264 2 5
⇒ 5x = 2x + 528
⇒ 5x – 2x = 528
⇒ x = 528 ÷ 3 = 176 m
 A train passes a 50 metres long platform in 14 seconds and a man standing on the platform in 10 seconds.The speed of the train is :

 24 km/hr
 36 km/hr
 40 km/hr
 45 km/hr

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Rule 10 and Rule 1,
Let the length of train be x metres
∴ According to questionSpeed of the train = x m/sec. 10
Also, the speed of the train= x + 50 m/sec. 14
[∵ It passes the platform in 14 seconds]
Both the speeds should be equal,
i.e.,x = x + 50 10 14
or 14x = 10x + 500
or 14x – 10x = 500
or 4x = 500
∴ x = 125 metresHence, Speed = 125 = 12 5. m/sec. 10 = 12.5 × 18 km/hr. 5
= 45 km/hr.Correct Option: D
Rule 10 and Rule 1,
Let the length of train be x metres
∴ According to questionSpeed of the train = x m/sec. 10
Also, the speed of the train= x + 50 m/sec. 14
[∵ It passes the platform in 14 seconds]
Both the speeds should be equal,
i.e.,x = x + 50 10 14
or 14x = 10x + 500
or 14x – 10x = 500
or 4x = 500
∴ x = 125 metresHence, Speed = 125 = 12 5. m/sec. 10 = 12.5 × 18 km/hr. 5
= 45 km/hr.