There are four bells which ring at an interval of 15 minutes, 25 minutes, 35 minutes and 45 minutes respectively. If <strong>ALL</strong> of them ring together at 9 A.M., how many more times will they ring together in the next 72 hours?
- A. 0
- B. 1
- C. 2 ✓
- D. 3
Correct Answer: C. 2
Explanation
The LCM of 15, 25, 35, 45 is 1575 minutes, which equals 26.25 hours. In the next 72 hours, they will ring together \lfloor \frac{72}{26.25} \rfloor = 2 times.
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