DATA SUFFICIENCY PROBLEMS ON TRAIN QUICK SOLVING TECHNIQUE

DATA SUFFICIENCY 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 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 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).