question_answer

Two men A and B are 2 km away from each other. At a certain moment A starts walking towards B at 2 kmph. At the same moment B starts walking towards A at 3 kmph and, after walking a certain distance, B increases his speed to 6 kmph and finally catches up with A. If B had walked each half of the distance covered by him at two different given speeds, what is the time taken by him to catch up with A?

Answer:

  Average speed of\[B=\frac{2\times 6\times 3}{6+3}=4kmph\] Relative speed\[=4+2=6\,kmph\] \[time=\frac{2}{6}=\frac{1}{3}hr\,\,or\,\,20\,\,\min \]