21.
A train moves with a speed of 108 kmph. Its speed in meters per second is:
• A.
10.8
• C.
30
• B.
18
• D.
38.8
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Explanation :

108 kmph =   108 x
 5 18
m/sec = 30 m/sec.

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22.
Two stations A and B are 110 km apart on a straight line. One train starts from A at 7 a.m. and travels towards B at 20 kmph. Another train starts from B at 8 a.m. and travels towards A at a speed of 25 kmph. At what time will they meet?
• A.
9 a.m.
• C.
10.30 a.m.
• B.
10 a.m.
• D.
11 a.m.
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Explanation :

Suppose they meet x hours after 7 a.m.

Distance covered by A in x hours = 20x km.

Distance covered by B in (x -1) hours = 25 (x � 1) km.

20x + 25 (x - 1) = 110     45x = 135     x = 3.

So, they meet at 10 a.m.

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23.
Two goods train each 500 m long, are running in opposite directions on parallel tracks. Their speeds are 45 km/hr and 30 km/hr respectively. Find the time taken by the slower train to pass the driver of the faster one.
• A.
12 sec
• C.
48 sec
• B.
24 sec
• D.
60 sec
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Explanation :

Relative speed = (45 + 30) km/hr =   75 x
 5 18
m/sec =
 125 6
m/sec.

Distance covered = (500 + 500) m = 1000 m.

Required time =   1000 x
 6 125
sec = 48 sec.

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24.
A train 108 m long moving at a speed of 50 km/hr crosses a train 112 m long coming from opposite direction in 6 seconds. The speed of the second train is
• A.
48 km/hr
• C.
66 km/hr
• B.
54 km/hr
• D.
82 km/hr
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Explanation :

Let the speed of the second train be x km/hr.

Relative speed = (x + 50) km/hr =   (x + 50) x
 5 18
m/sec =

 250 + 5x 18

m/sec.

Distance covered = (108 + 112) = 220 m.

220

 250 + 5x 18

=  6 250 + 5x = 660 x = 82 km/hr.

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25.
The length of a train and that of a platform are equal. If with a speed of 90 km/hr, the train crosses the platform in one minute, then the length of the train (in metres) is:
• A.
500
• C.
750
• B.
600
• D.
900
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Explanation :

Speed =   90 x
 5 18
m/sec = 25 m/sec; Time = 1 min. = 60 sec.

Let the length of the train and that of the platform be x metres.

Then,
 2x 60
= 25 x =
 25 x 60 2
= 750.

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