Mathematics
NULL
Medium
Question
A and B walk opposite ways on a circular track at 2 and 3 rounds per hour. Starting together at 8 a.m., how many times do they cross before 9:30 a.m.?
A
5
B
6
C
7
✓ Official correct answer
D
8
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A
5
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B
6
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C
7
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D
8
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Explanation
Relative speed = 2 + 3 = 5 rounds/hour. From 8:00 to 9:30 is 1.5 hours ⇒ crossings before 9:30 = 5 × 1.5 = 7.5, so they meet 7 times before 9:30 (the half-meeting falls exactly at 9:30).