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by [email protected] » Sun Jun 27, 2010 8:02 pm
A train 120 meters long passes an electric pole in 12 seconds and another train of same length traveling in
opposite direction in 8 seconds. The speed of the second train is
A. 60 Km
B. 66 Km
C. 72 Km
D. 80 Km
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Source: — Problem Solving |

by Rahul@gurome » Sun Jun 27, 2010 8:41 pm
Solution.
The train which is 120 metres in length crosses a pole in 12 seconds implies it is covering the distance 120 metres in 12 seconds.
So speed of this train is 120/12 = 10 m/s.
It is crossing another train traveling in opposite direction in 8 seconds.
Let the speed of this train be y.
It's length is also 120 metres.
So (120+120)/(10+y) = 8.
Or 10+y = 30.
Or y = 20 m/s or 20*18/5 km/hr = 72 km/hr

The correct answer is C.
Rahul Lakhani
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by pradeepkaushal9518 » Mon Jun 28, 2010 12:02 am
its no clear from question that the second train cross what in 8 sec the pole or first train?
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