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 2 rounds per hour and 2 rounds per hour respectively. How many times shall they cross each other before 9.30 a.m. ?
Choose the correct choice from the following answers.
A) A)5
B) B)61
C) C)8
D) D)6
E) E)9
Relative speed = 2 + 2= 
<gadget id="calculator">2 + 2</gadget>
<output>4</output>
4 rounds per hour.   So, they cross each other 4 times in an hour and 2 times in half an hour.   Hence, they cross each other 6 times before 9.30 a.m.   ANSWER:6
<result>D</result>
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 2 rounds per hour and 2 rounds per hour respectively. How many times shall they cross each other before 9.30 a.m. ?