Two bells ring together at 12:00. One rings every 6 minutes and the other every 8 minutes. Counting 12:00 and 14:00, how many times do they ring together between 12:00 and 14:00?
Answer and explanation
Correct answer: B. 6
- Step 1: They ring together every LCM(6, 8) = 24 minutes.
- Step 2: From 12:00 to 14:00 is 120 minutes, and 120 / 24 = 5 gaps.
- Step 3: With both end times counted there are 5 + 1 = 6 times.
Answer
6.
Why not the others: 5 forgets to count the first ring at 12:00, 4 and 7 come from using the wrong gap or an extra ring.
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