www ssc.nic.in ssc LDC/DEO exam solved maths paper 2012

Wednesday, 7 November 2012

ssc LDC/DEO exam solved maths paper 2012

 
1.  A train running at the speed of 60 km/hr crosses a pole in 9 seconds. What is the length of the train?

A. 120 metres B. 180 metres
C. 324 metres D. 150 metres

Answer  Option D
Explanation:

Speed=   60 x 5 m/sec =  50 m/sec.
18 3

Length of the train = (Speed x Time) =  50 x 9 m = 150 m.
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2.  A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is:

A. 45 km/hr B. 50 km/hr
C. 54 km/hr D. 55 km/hr

Answer & ExplanationAnswer: Option B
Explanation:

Speed of the train relative to man =  125 m/sec
10

   =  25 m/sec.
2

   =  25 x 18 km/hr
2 5

   = 45 km/hr.
Let the speed of the train be x km/hr. Then, relative speed = (x - 5) km/hr.
 x - 5 = 45          x = 50 km/hr.
 
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3.  The length of the bridge, which a train 130 metres long and travelling at 45 km/hr can cross in 30 seconds, is:

A. 200 m B. 225 m
C. 245 m D. 250 m

Answer & ExplanationAnswer: Option C
Explanation:

Speed =  45 x 5 m/sec =  25 m/sec.
18 2

Time = 30 sec.
Let the length of bridge be x metres.
Then, 130 + x = 25
30 2

 2(130 + x) = 750
 x = 245 m.
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4.  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 B. 3 : 2
C. 3 : 4 D. None of these

Answer & ExplanationAnswer: Option 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 = 23
x+ y

 27x + 17y = 23x + 23y
 4x = 6y
  x = 3 .
y =2

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5.  A train passes a station platform in 36 seconds and a man standing on the platform in 20 seconds. If the speed of the train is 54 km/hr, what is the length of the platform?

A. 120 m B. 240 m
C. 300 m D. None of these