Equally sharing a cake between three people - Numberphile

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  • Published on Sep 26, 2017

  • Audible (30-day trial, free audio book): https://www.audible.com/numberphile More links & stuff in full description below ↓↓↓ This video features Dr Hannah Fry. More videos with Hannah: http://bit.ly/hannah_vids Hannah's website: http://www.hannahfry.co.uk Her book mentioned is "The Mathematics of Love". Envy free cake cutting (the paper mentioned): https://arxiv.org/abs/1604.03655 A clarifying note from Hannah: n^n^n^n^n^n is the maximum number of cuts in the n person case. Something we could have made clearer... Bob's trimmed piece still carries the status of his "first choice", so if Charlie leaves it, Bob will (must) pick it... otherwise he'll pick the one that was his original "second choice"... The upshot of this is that there's no chance Alice will be left with the trimmed piece after everyone takes their first piece. And Bob remains envy free under these conditions too. A trilogy of mathematical cake cutting videos... http://bit.ly/CakeCuttingTrilogy Editing and animation in this video by Pete McPartlan Discuss this video on Brady's subreddit: https://redd.it/72jyww Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile We are also supported by Science Sandbox, a Simons Foundation initiative dedicated to engaging everyone with the process of science. NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile tweets: https://twitter.com/numberphile Subscribe: http://bit.ly/Numberphile_Sub Videos by Brady Haran Patreon: http://www.patreon.com/numberphile Brady's videos subreddit: http://www.reddit.com/r/BradyHaran/ Brady's latest videos across all channels: http://www.bradyharanblog.com/ Sign up for (occasional) emails: http://eepurl.com/YdjL9
  • Equally sharing a cake between three people - Numberphile etiketleri


  • No friends = No problems

  • I'd just blend it, and divide by weight....

  • The one who has the knife , gets the whole cake .

  • So this is what people who write exam questions spend their time doing

  • and this is why socialism doesn't work

  • Cake?! Should've been

  • the title of this video is wrong. the exercise is not about getting equal slices but about satisfying preferences.

  • Moral: never share cake with a mathematician

  • Amazing unintentional ASMR in this video.

  • Easiest solution to make a fair cut: Alice cuts and passes the piece. If both Bob and Charlie don't accept it, then Alice gets the piece. Then Bob cuts and Charlie either accepts or not. This way you can't get a large piece unless others agree to it.

  • This is why you never invite a mathematician to a birthday party.


  • 1:21

  • Aka "how to divvy up weed without scales".

  • Just cut it into equal pieces of 12 and everyone take 4 each

  • Just cut it well and don't complain. Solved

  • So, let's say Charlie takes the "Dud" piece, then, Bob, seeing the trimmed and untrimmed slices as being equal, takes the untrimmed piece, would that not make Alice unhappy due to getting a piece with some cake trimmed off? Or is that in the rules, Bob must take the piece he trimmed if it is available?

  • The cake is a lie.

  • Why not just cut into 6 then have 2 slices