Question

A and B walk around a circular track. They start at 8 a.m. from the same point in the
opposite directions. A and B walk at a speed of 6 rounds per hour and 4 rounds per hour
respectively. How many times shall they cross each other before 11.45 a.m. (approx)?​

Answer 1

Answer:

7 times

Step-by-step explanation:

Let us treat circular motion in degrees. 1 round = 360°

Speed of A

= 2 round/hr. = 720° in 60 min = 360° in 30 min

= (360°/30) in 1 min.

= 12° / min.

Speed of B

= 3 round/hr. = 1080° in 60 min = 540° in 30 min

= (540°/30) in 1 min.

= 18° / min.

Since A and B are moving in the opposite directions, they complete 360° together, while crossing each other.

Let it take n minutes to make a round (360°) together.

n (12°+18°) = 360°

n=360°/30°

n=12

They cross each other once in 12 minutes.

Between 8:00 am to 9:30 am, there are 90 minutes.

The number of crosses = 90/12 = 7.5

Ans: They will cross each other 7 times before 9.30 am