Multiple choice

Three clocks were set to true time. First runs with the exact time. Second slows one minute/day. Third gains one minute/day. After how many days will they show true time again?

  1. 360

  2. 180

  3. 720

  4. 480

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The second clock loses 1 minute per day, and the third gains 1 minute per day. For a clock to show the true time again, it must lose or gain exactly 12 hours (720 minutes). Since the clocks change by 1 minute per day, it takes 720 days for them to accumulate a 720-minute difference.

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