A and B walk around a circular track. They start at 9 a.m. 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 before 12:00 P.m.?
Options
A) 28  B) 27  C) 26  D) 25  E) 20
Sol.   Relative speed = (2 + 3)= 
<gadget id="calculator">(2 + 3)</gadget>
<output>5</output>
5 rounds per hour.   So, they cross each other 5 times in an hour.   Hence, they cross each other 20 times before 12:00 P.m.   Answer 20
<result>E</result>
A and B walk around a circular track. They start at 9 a.m. 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 before 12:00 P.m.?