Two men start from points A and B respectively, 42 km apart. One walks from A to B at 4 km/hr and another walks from B to A at a certain uniform speed. They meet each other after 6 hours. Find the speed of the second man.

Distance between the two men = 42 km

Speed of man at point A = 4 km/hr

Speed of man at point B = 4 km/hr (say)

Time = 6 hrs

⇒ Relative speed = 7 km/hrs

Speed of man at point B = Relative speed – Speed of man at point A

= 7 km/hrs – 4 km/hr

= 3 km/hrs

Therefore, speed of second man is 3 km/hrs