376. A train with a uniform speed passes a platform, 122 metres long, in 17 seconds and a bridge, 210 metres long, in 25 seconds. The speed of the train is

1. 1. 46.5 km/hour

   
   
   

   2. 37.5 km/hour

   
   
   

   3. 37.6 km/hour

   
   
   

   4. 39.6 km/hour

   
   
   

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1. View Hint View Answer Discuss in Forum

   Let the length of the train be x
   According to the question,
   

   x + 122	=	x + 210
   17		25

   
   ⇒  25x + 3050 = 17x + 3570
   ⇒  25x – 17x = 3570 – 3050
   ⇒  8x = 520
   

   ⇒  x =	520	= 65 metres
   	8

   
   

   ∴  Speed of the train =	65 + 122
   	17

   
   

   =	187	metre/second
   	17

   
   = 11 metre/second
   

   =	11 × 18	kmph
   	5

   
   = 39.6 kmph

   Correct Option: D

   Let the length of the train be x
   According to the question,
   

   x + 122	=	x + 210
   17		25

   
   ⇒  25x + 3050 = 17x + 3570
   ⇒  25x – 17x = 3570 – 3050
   ⇒  8x = 520
   

   ⇒  x =	520	= 65 metres
   	8

   
   

   ∴  Speed of the train =	65 + 122
   	17

   
   

   =	187	metre/second
   	17

   
   = 11 metre/second
   

   =	11 × 18	kmph
   	5

   
   = 39.6 kmph

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377. A train, with a uniform speed, crosses a platform, 162 metres long, in 18 seconds and another platform, 120 metres long, in 15 seconds. The speed of the train is

1. 1. 14 km/hr

   
   
   

   2. 42 km/hr

   
   
   

   3. 50.4 km/hr

   
   
   

   4. 67.2 km/hr

   
   
   

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1. View Hint View Answer Discuss in Forum

   Let the Length of the train be x
   

   Then,	x + 162	=	x + 120
   	18		15

   
   (Speed of the train)
   

   ⇒	x + 162	=	x + 120
   	6		5

   
   ⇒  6x + 720 = 5x + 810
   ⇒  x = 810 – 720 = 90
   

   ∴  Speed of the train =	90 + 162	m/sec.
   	18

   
   

   =	252	×	18	kmph
   	18		5

   
   = 50.4 kmph

   Correct Option: C

   Let the Length of the train be x
   

   Then,	x + 162	=	x + 120
   	18		15

   
   (Speed of the train)
   

   ⇒	x + 162	=	x + 120
   	6		5

   
   ⇒  6x + 720 = 5x + 810
   ⇒  x = 810 – 720 = 90
   

   ∴  Speed of the train =	90 + 162	m/sec.
   	18

   
   

   =	252	×	18	kmph
   	18		5

   
   = 50.4 kmph

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378. A train travelling with uniform speed crosses two bridges of lengths 300 m and 240 m in 21
     seconds and 18 seconds respectively. The speed of the train is :

1. 1. 72 km/hr

   
   
   

   2. 68 km/hr

   
   
   

   3. 65 km/hr

   
   
   

   4. 60 km/hr

   
   
   

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1. View Hint View Answer Discuss in Forum

   Let the length of the train be x.
   

   ∴  Speed of the train =	x + 300	=	x + 240
   	21		18

   
   

   ⇒	x + 300	=	x + 240
   	7		6

   
   ⇒  7x + 1680 = 6x + 1800
   ⇒  x = 120
   

   ∴  Speed of the train =	x + 300	=	420	= 20 m/sec
   	21		21

   
   

   =		20 × 18		kmph = 72 kmph
   		5

   Correct Option: A

   Let the length of the train be x.
   

   ∴  Speed of the train =	x + 300	=	x + 240
   	21		18

   
   

   ⇒	x + 300	=	x + 240
   	7		6

   
   ⇒  7x + 1680 = 6x + 1800
   ⇒  x = 120
   

   ∴  Speed of the train =	x + 300	=	420	= 20 m/sec
   	21		21

   
   

   =		20 × 18		kmph = 72 kmph
   		5

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379. A train, 110m long , is running at a speed of 60km/hr. How many seconds does it take to
     cross another train, 170 m long, standing on parallel track ?

1. 1. 15.6 sec

   
   
   

   2. 16.8 sec

   
   
   

   3. 17.2 sec

   
   
   

   4. 18 sec

   
   
   

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1. View Hint View Answer Discuss in Forum

   Speed of train =	Sum of length of both trains
   	Time taken

   
   

   ⇒	60 × 5	=	110 + 170	=	280
   	18		t		t

   
   

   ⇒ t =	280 × 18	= 16.8 seconds.
   	60 × 5

   Correct Option: B

   Speed of train =	Sum of length of both trains
   	Time taken

   
   

   ⇒	60 × 5	=	110 + 170	=	280
   	18		t		t

   
   

   ⇒ t =	280 × 18	= 16.8 seconds.
   	60 × 5

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380. A train of length 500 feet crosses a platform of length 700 feet in 10 seconds. The speed of the train is

1. 1. 70 ft/second

   
   
   

   2. 85 ft/second

   
   
   

   3. 100 ft/second

   
   
   

   4. 120 ft/second

   
   
   

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1. View Hint View Answer Discuss in Forum

   Speed of train =	Length of (train + platform)
   	Time taken to cross

   
   

   =		500 + 700		feet/second = 120 feet/second
   		10

   
   Second Method :
   Here, x = 500 feet, y = 700 feet
   t = 10 seconds, u = ?
   using
   

   t =	x + y
   	u

   
   

   u =	500 + 700
   	10

   
   = 120ft/second

   Correct Option: D

   Speed of train =	Length of (train + platform)
   	Time taken to cross

   
   

   =		500 + 700		feet/second = 120 feet/second
   		10

   
   Second Method :
   Here, x = 500 feet, y = 700 feet
   t = 10 seconds, u = ?
   using
   

   t =	x + y
   	u

   
   

   u =	500 + 700
   	10

   
   = 120ft/second

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