A and B walk around a circular track. A and B walk at a speed of 2 rounds per hour and 3 rounds per hour respectively. If they start at 8 a.m. from the same point in opposite directions, how many times shall they cross each other before 9.30 a.m.?	Choose the correct answer.
A) 5  B) 6  C) 7  D) 8  E) 9
Explanation:   Relative speed = Speed of A + Speed of B (∴ they walk in opposite directions)   =2+3= 
<gadget id="calculator">2+3</gadget>
<output>5</output>
5 rounds per hour   Therefore, they cross each other 5 times in 1 hour and 2 times in 12 hour   Time duration from 8 a.m. to 9.30 a.m.=1.5 hour   Hence they cross each other 7 times before 9.30 a.m.   ANSWER IS 7
<result>C</result>
A and B walk around a circular track. A and B walk at a speed of 2 rounds per hour and 3 rounds per hour respectively. If they start at 8 a.m. from the same point in opposite directions, how many times shall they cross each other before 9.30 a.m.?