A person X starts from a place A and another person Y starts simultaneously from another place B which is d km away from A. They walk in the same direction. X walks at an average speed of u km/hr and Y walks at an average speed of v km/hr. How far will X have walked before he overtakes Y?

  1. A. \frac{ud}{(u-v)}
  2. B. \frac{vd}{(u-v)}
  3. C. \frac{(ud-vd)}{(u-v)}
  4. D. \frac{(ud+vd)}{(u+v)}

Correct Answer: A. \frac{ud}{(u-v)}

Explanation

Relative speed of X with respect to Y is (u-v)\text{ km/hr}. The time taken to cover the initial gap d is t = \frac{d}{u-v} hours. Distance covered by X in this time is u \times t = \frac{ud}{u-v}.

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