QUESTION

CSAT

Medium

Maths

Prelims 2016

A and B walk around a circular park. They start at 8 am from the same point in the 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 after 8:00 am and before 9:30 am?

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Explanation

A's speed = $2$ rounds per hour B's speed = $3$ rounds per hour Total time = 9:30 am - 8:00 am = $1.5$ hours Steps: Relative speed of A and B: $2+3$ Result: $5$ rounds per hour

Time period = $1.5$ hours

Number of crossings: Since A and B move in opposite directions, the number of times they cross each other in $1.5$ hours is given by: $5 \times 1.5$ Result: $7$ times