Beach Day by Rodger Bliss
September 2023

Bad Clock Riddle

You have the misfortune to own an unreliable clock. This one loses exactly 24 minutes every hour. It is now showing 3:00am and you know that is was correct at midnight, when you set it.

The clock stopped 1 hour ago, what is the correct time now?

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5 guesses to Bad Clock Riddle

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  • Crabman

    It is 6am.

    Saying “Loses 24 minutes”, is another way of saying “Moves 36 minutes every hour”. 36 is 60% of 60, so its moving at 60% speed. For the clock to progress 3 hours, 5 hours would need to have passed (3 is 60% of 5). So at 5am, the clock would have struck 3:00, and that was one hour ago so it is 6am now.

  • brent

    I agree with Taylor and Crabman has a good explanation of why that might be the case.
    But also it could currently be 2 PM or 10 PM.

    To get the current time as 10 PM, you would have set the clock to midnight almost two full days ago (46 hours ago). The clock would have run at 60% of its speed for 45 hours – which would have been 27 hours at 60% time. Then because it stopped an hour ago, it would now be 46 hours later or 10 PM.

    If the clock thinks it has run for 48 + 3 hours since you set it at midnight, it would have run for 51 hours at 60% speed, or 85 hours of “real time” before stopping an hour ago, so then the current time would be 2:00 PM a little more than 3.5 days after setting the clock.

    If the clock thinks it has run for 72 hours (or any other multiple of 3 full days including 0 days) before stopping to show 3AM 1 hour ago, the current time will be 6 AM.

    Note the 10:00 PM and 2:00 PM situations would also re-occur depending how many full days the clock “thinks” it has run before stopping at 3:00 AM.

    Changing your own time zone, going on, or off daylight savings time could all shift the answer to this riddle.

  • Taylor, you are today’s winner!
    6:00am: since the clock is losing 24 minutes every hour, for every real hour that has passed, the clock will only show 36 minutes. Since the clock shows 3:00am, we know that 180 clock minutes have passed. This therefore equals 300 real minutes and hence 5 hours. The clock stopped 1 hour ago and the time must now be 6.00am.