11.
In what time will a train 100 metres long cross an electric pole, if tis speed be 144 km/hr?
• A.
2.5 seconds
• C.
5 seconds
• B.
4.25 seconds
• D.
12.5 seconds
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Explanation :

Speed =   144 x
 5 18
m/sec = 40 m/sec.

Time taken =
 100 40
sec = 2.5 sec.

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12.
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?
• A.
69.5 km/hr
• C.
79 km/hr
• B.
70 km/hr
• D.
79.2 km/hr
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Explanation :

Let the length of the train be x metres and its speed by y m/sec.

They,
 x y
= 8  x = 8y

Now,
 x + 264 20
= y 8y + 264 = 20y  y = 22.

Speed = 22 m/sec =   22 x
 18 5
km/hr = 79.2 km/hr.

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13.
Two trains, each 100 m long, moving in opposite directions, cross each other in 8 seconds. If one is moving twice as fast the other, then the speed of the faster train is:
• A.
30 km/hr
• C.
60 km/hr
• B.
45 km/hr
• D.
75 km/hr
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Explanation :

Let the speed of the slower train be x m/sec.

Then, speed of the faster train = 2x m/sec.

Relative speed = (x + 2x) m/sec = 3x m/sec.

 (100 + 100) 8
= 3x 24x = 200 x =
 25 3

So, speed of the faster train =
 50 3
m/sec =
 50 3
x
 18 5
km/hr = 60 km/hr.

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14.
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
• C.
300 m
• B.
240 m
• D.
None of these
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Explanation :

Speed =   54 x
 5 18
m/sec = 15 m/sec.

Length of the train = (15 x 20) m = 300 m.

Let the length of the platform be x meters.

Then,
 x + 300 36
= 15 x + 300 = 540 x = 240 m.

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15.
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 meters
• C.
324 meters
• E.
None of these
• B.
180 meters
• D.
Cannot be determined
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Explanation :

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

Length of the train = (Speed x Time) =
 50 3
x 9    m = 150 m.

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