School-Safe Puzzle Games

When Did it Happen?

My wife and I both left the house around 8:00 AM, she went to work and I left to do some errands.  When I got back home, I found the following:

-My oven clock was showing 11:12.

-My coffee maker was displaying a blinking 1:36 AM.

-My cable box was showing the correct time of 1:24 PM.

After a few minutes with pen and paper, I pulled out my cell phone and sent a text to my wife, letting her know the exact times when the power went out and came back on again.

What were those times, and how did I figure it out?

(We can assume, for this problem, that all clocks were displaying the correct time when the power outage occurred)

Thanks to Bobo for sending this -inspired by actual events that took place in early November!

Answers to this challenge can be entered into the section below; submissions will automatically be revealed when time is up!


12 Comments to “When Did it Happen?”

  1. .mau. | Profile

    The coffee maker restarted from 12:00AM when the power went up again, therefore it must have been 96 minutes before, at 11:48AM.

    The oven clock presumably was stopped while there was no power, so the outage time must have been 2h12′ and therefore started at 9:36AM… unless it just stopped working at 11:12 at the start of the power outage, and did not resume working automatically.

  2. ospitada | Profile

    The cable clock reset itself. The coffee maker resets to 12:00 AM, which shows that the power went out 1 hour and 36 minutes ago. Subtracting that from the cable time you get 12:48, which is the same time the oven clock (presumably some sort of flip clock that doesn’t reset) gives you if you add 1 hour and 36 minutes to it.

  3. John Lewis Highsmith | Profile

    The coffee maker clock, a digital, reset to 0000 (ok it was 12:00)when the power was restored. It, and the other clocks, had run for 1h 36m from the time of restart until the person viewed them.

    The oven clock was not digital and restarted displaying the same time as it had when the power went off. It ran 1h 36 min from that time to the 1112 displayed. This gives us 0936 as the power-off time.

    The cable box had reset to the correct time, 1324, at power-on, since its displayed time is controlled by the cable system. Going back 1h 36m from that time gives 1148 as the power-on time.

    And as we say in the land of geometry: Flatland, Euclidian, or otherwise, QED.

  4. engjs1960 | Profile

    The Coffee Maker reset to 12am, so the power came on at 11:48am. The oven clock just picked up from where it stopped, so the power was out for 2 hours 12 minutes. So the power went off at 9:36am.

  5. cheddarmelt | Profile

    Assuming that the oven clock is not digital, and therefore tracks total time plugged in, but that the coffee maker clock IS digital and tracks time starting at 12:00 AM when powered on, we can calculate the following:

    13:24 (current time) – 1:36 (time on coffee maker) = 11:48 (time power came on).
    13:24 (current time) – 11:12 (amount of time electricity has been on since midnight) = 2:12 (total time electricity was out).

    11:48 (time power came on) – 2:12 (blackout duration) = 9:36 (time power went out).

    So, power went out at 9:36 AM and came back on at 11:48 AM.

  6. Pookah | Profile

    off at 9:36; on at 11:48

  7. Bobo The Bear | PUZZLE MASTER | Profile

    Nicely done, all. The power outage described actually took place for me on November 16th (nothing like on the east coast, though). Those were the real times that were displayed. And yes, I sat down with pen and paper and figured out when the power outage began (9:36 AM) and ended (11:48 AM) before I went around resetting all the clocks in the house.

  8. Hex | PUZZLE MASTER | Profile

    I missed that puzzle unfortunately.

    But assuming that the coffee maker has an electronic clock that resets itself to 00:00 upon powering up, and that the oven clock is an electrically driven mechanical clock that just pauses while the electricity is out, we can deduce:
    – The coffee maker shows that the power was back 1 hour 36 min ago
    – Since the actual time was 1:24PM, then the power must have come back at 11:48AM
    – The oven shows a delay of 1:24PM – 11:12AM = 2 hour 12 minutes and hence the power outage lasted that long
    – Since the power was restored at 11:48AM, then it must have started at 9:36AM

  9. Chris Edwards | Profile

    x = time power went out
    y = time electricity restored

    t = current time = 13:24
    o = oven display = 11:12
    total time power out = t – o = 13:24 – 11:12 = 2:12

    time since restart = coffee display = 1:36

    y = t – 1:36 = 11:48
    x = y – (t – o) = 11:48 – 2:12 = 9:36
    x = off 9:36
    y = on 11:48

  10. Chris Edwards | Profile

    @Pookah: I love your eloquent and concise answer. And yer foto!

  11. Minimoomadi | Profile

    9:32 a.m.
    12:34 p.m.

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