A and B walk around a circular track they start at 8 am from the same point in opposite directions A and B walk at a speed of 2 rounds per hour and 3 rounds per hour respectively. How many times shall they cross each other before 9:30 am?

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answer is B.

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Detailed Solution

Concept: In this question, A's relative velocity to B is 5 laps per hour. This will cause A to cross B five times an hour. Therefore, calculate the time from 8 am to 9:30 am and apply a consistent method to get the total number of intersections within that time frame.
Given, Walk at a speed of 2 laps an hour. And B goes at a speed of 3 rounds an hour. But given that they are moving in the opposite direction from the same point. Therefore, the relative speed of A and B is

laps per hour (the "+" sign is in the opposite direction when moving in the same direction as the "-" sign is displayed. Because it is moving.) This means that A and B intersect 5 times an hour.
Now, given that they start at 8am, we need to find out how many times they will cross by 9:30 am (i.e. within 1. 5 hours). That is, it crosses 5 times in an hour, so it crosses at least 2 times in 30 minutes (because 2. 5 is not possible and 3 cannot be taken). Therefore, in an hour and a half, they intersect each other

Therefore, it will cross 7 times by 9:30 am.
Hence, the correct answer is option (2).

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