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  1. What is the speed of the train whose length is 210 metres?

    I. 

    The train crosses another train (Howrah Express/12869) of 300 metres length running in opposite direction in 10 seconds.

     II. 

    The train crosses another train (Howrah Express/12869) running in the same direction at the speed of 60 km/hr in 30 seconds.

  2. A.

    I alone sufficient while II alone not sufficient to answer

    B.
    II alone sufficient while I alone not sufficient to answer
    C.
    Either I or II alone sufficient to answer
    D.
    Both I and II are not sufficient to answer
    E.
    Both I and II are necessary to answer

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    Answer : Option E

    Explanation :

     

    Time taken to cross the train,
    running in opposite directions
    =\({ (l1 + l2) \over (u + v)}sec\)   .
     

     

     \(10= {(210 + 300) \over (u + v)}\)  
     

        u + v = 51.

     

    Time taken to cross the train, running in same direction    \(= {(l1 + l2) \over (u - v)} sec\)sec.
     

     

     30 = \({(210 + 300) \over (u - 60 \times )(5/18)}\)  
     

     

     u =       \( (17+\frac{50}{3})m/sec\)
     

     

    Thus, u and v can be obtained.

     

     Correct answer is (E).

     


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