A and B start from the same point and in the same direction at 7 a.m. to walk around a rectangular field (400 m ☓ 300 m). A and B walk at the rate of 3 km/hr and 2.5 km/hr respectively. How many times shall they cross each other if they continue to walk till 12 : 30 p.m.?
Note
Perimeter of the field = 2(400 + 300)m = 1400 m = 1.4 km.
Since A and B move in the same direction, so they will first meet each other when there is a difference of one round. i.e., 1.4 km between the two.
The relative speed of A and B = (3 – 2.5) km/hr = 0.5 km/hr.
Time is taken to cover 1.4 km at this speed = 2 hr 48 min.
So, they shall first cross each other at 9 : 48 a.m. and again, 2 hr 48 min after 9 : 48 a.m. i.e., 12 : 36 p.m.
Thus, till 12 : 30 p.m. they will cross each other once.