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16.
Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 23 seconds. The ratio of their speeds is:
  • A.
    1:3
  • C.
    3:4
  • B.
    3:2
  • D.
    None of these
  • Answer & Explanation
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Answer : [B]
Explanation :
 
Let the speeds of the two trains be x m/sec and y m/sec respectively. Then,
 
Length of the first train = 27x metres, and length of the second train = 17y metres.
 
 
 
27x + 17y
x + y
 = 23
 
27x + 17y = 23x + 23y
 
4x = 6y
 
x
y
=
3
2
 
 
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17.
A train 110 m long passes a man, running at 6 kmph in the direction opposite to that of the train, in 6 seconds. The speed of the train is:
  • A.
    54 km/hr
  • C.
    66 km/hr
  • B.
    60 km/hr
  • D.
    72 km/hr
  • Answer & Explanation
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Answer : [B]
Explanation :
 
Speed of the train relative to man =  
110
6
   m/sec =  
110
6
x
18
5
   km/hr = 66 km/hr.    
 
Let the speed of the train be x kmph. Then, relative speed = (x + 6) = kmph.
 
 
  x + 6 = 66  or  x = 60 kmph.      
 
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18.
A 300 metre long train crosses a platform in 39 seconds while it crosses a signal pole in 18 seconds. What is the length of the platform?
  • A.
    320 m
  • C.
    650 m
  • B.
    350 m
  • D.
    500 m
  • Answer & Explanation
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Answer : [B]
Explanation :
 
Speed =  
300
18
   m/sec =
50
3
 m/sec.  
 
Let the length of the platform be x metres
 
Then,
x + 300
39
=
50
3
 
 3 (x + 300) = 1950
 
x = 350 m.    
 
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19.
A train 280 m long, running with a speed of 63 km/hr will pass a tree in:
  • A.
    15 sec
  • C.
    18 sec
  • B.
    16 sec
  • D.
    20 sec
  • Answer & Explanation
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Answer : [B]
Explanation :
 
Speed =   63 x
5
18
   m/sec =
35
2
 m/sec.
 
Time taken =   280 x
2
35
   sec = 16 sec.    
 
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20.
A train 125 m long passes a man, running at 5 kmph in the same direction in which the train is going, in 10 seconds. The speed of the train is:
  • A.
    45 km/hr
  • C.
    54 km/hr
  • B.
    50 km/hr
  • D.
    55 km/hr
  • Answer & Explanation
  • Report
Answer : [B]
Explanation :
 
Speed of the train relative to man =  
125
10
   m/sec =  
25
2
   m/sec.      
 
=   
25
2
x
18
5
   km/hr = 45 km/hr.    
 
Let the speed of the train be x kmph. Then, relative speed = (x – 5) kmph.
 
 
  x - 5 = 45  or   x = 50 kmph.  
 
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