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Joined 4 months ago
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Cake day: February 21st, 2026

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  • I know a couple of math tricks you can do with playing cards.

    • Give an audience member a pre-sorted deck of cards. Remove any card. Riffle shuffle the deck 3 times (4 if you’re bold). Return the removed card to a random position in the deck. Magician examines the deck and identifies the card.

    • Audience member selects any 5 cards and hands them the the magician’s beautiful assistant. Assistant examines these cards, and reveals 4 of them, one at a time, to the magician. Magician predicts the 5th card.


  • crwth@piefed.ziptoScience Memes@mander.xyz$1$
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    25 days ago

    I had a student tasked with summing a finite geometric sequence with |r|>1, let’s say 1+2+4+8+16. He had apparently forgotten the formula for that, but knew the formula for the infinite series a/(1-r). Good enough he thinks, and sums 1+2+4+… = -1, then subtracts off the excess terms 32+64+128+… = -32, and gets the correct answer of 31.








  • crwth@piefed.ziptoAsk Lemmy@lemmy.world*Permanently Deleted*
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    3 months ago

    I flooded a dormitory once, but I blame building maintenance for tricking me into it.

    I wake up and head to the bathroom. Turn on the shower, nothing happens. Try the sink, still no water. No advance notice to the residents, but the water must have been shut off for some reason. I have a class to go to, so I turn everything “off”, get dressed, and leave. I’d forgotten that one of the sink knobs was threaded the opposite way from the standard convention, so that one was full on when the water was restored. Came back to the dorm after lunch and realized exactly what I’d done as soon as I entered the hallway and saw the maintenance man running his shop-vac outside my room. It overflowed the sink drain, and the bathroom floor drain, flowed through the dorm room, and was in the process of flooding the hallway.