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Problems on Trains - General Aptitude

Each of the questions given below consists of a statement and / or a question and two statements numbered I and II given below it. You have to decide whether the data provided in the statement(s) is / are sufficient to answer the given question. Read the both statements and
  • Give answer (A) if the data in Statement I alone are sufficient to answer the question, while the data in Statement II alone are not sufficient to answer the question.
  • Give answer (B) if the data in Statement II alone are sufficient to answer the question, while the data in Statement I alone are not sufficient to answer the question.
  • Give answer (C) if the data either in Statement I or in Statement II alone are sufficient to answer the question.
  • Give answer (D) if the data even in both Statements I and II together are not sufficient to answer the question.
  • Give answer(E) if the data in both Statements I and II together are necessary to answer the question.
Q1:

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.

A I alone sufficient while II alone not sufficient to answer

B II alone sufficient while I alone not sufficient to answe

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

ANS:E - Both I and II are necessary to answer

Time taken to cross the train,
running in opposite directions		 = (l1 + l2) sec.
(u + v)
 10 = (210 + 300)
(u + v)
    u + v = 51.
Time taken to cross the train, running in same direction = (l1 + l2) sec.
(u - v)
 30 = (210 + 300)
(u - 60 x (5/18))
 u = 17 + 50 m/sec.
3
Thus, u and v can be obtained.  Correct answer is (E).