How To Split A Cake Fairly Using Math

Share it with your friends Like

Thanks! Share it with your friends!

Close

How can 2 people split up a cake, knowing that each person wants to get a larger piece than the other? What about 3 people, or even N people? This is an example of a fair division problem from game theory. There are many cake-cutting algorithms to produce a fair solution mathematically. In this video I describe the “I cut, you choose” method and the “last diminisher method.”

Blog post: http://wp.me/p6aMk-4pX

If you like my videos, you can support me at Patreon: http://www.patreon.com/mindyourdecisions

Connect on social media. I update each site when I have a new video or blog post, so you can follow me on whichever method is most convenient for you.

My Blog: http://mindyourdecisions.com/blog/
Twitter: http://twitter.com/preshtalwalkar
Facebook: https://www.facebook.com/pages/Mind-Your-Decisions/168446714965
Google+: https://plus.google.com/108336608566588374147/posts
Pinterest: https://www.pinterest.com/preshtalwalkar/
Tumblr: http://preshtalwalkar.tumblr.com/
Instagram: https://instagram.com/preshtalwalkar/
Patreon: http://www.patreon.com/mindyourdecisions

Newsletter (sent about 2 times a year): http://eepurl.com/KvS0r

My Books

Here’s a listing of all my books
http://goo.gl/BDlEkB

Here’s a more detailed description of each book…

“The Joy of Game Theory” shows how you can use math to out-think your competition. (rated 4/5 stars on 21 reviews) http://amzn.to/1uQvA20

“Math Puzzles Volume 1” features classic brain teasers and riddles with complete solutions for problems in counting, geometry, probability, and game theory. Volume 1 is rated 4.6/5 stars on 9 reviews. http://amzn.to/1GhUUSH

“Math Puzzles Volume 2” is a sequel book with more great problems. http://amzn.to/1NKbyCs

“Math Puzzles Volume 3” is the third in the series. http://amzn.to/1NKbGlp

“40 Paradoxes in Logic, Probability, and Game Theory” contains thought-provoking and counter-intuitive results. (rated 4.9/5 stars on 7 reviews) http://amzn.to/1LOCI4U

“The Best Mental Math Tricks” teaches how you can look like a math genius by solving problems in your head http://amzn.to/18maAdo

“Multiply Numbers By Drawing Lines” This book is a reference guide for my video that has over 1 million views on a geometric method to multiply numbers. http://amzn.to/XRm7M4

Comments

Michael Wong says:

Thats not a pie its a cake

Babbaj3212 says:

i cut my cake concentrically

Feral Device says:

Last person gets a pile of crumbs.

ahmad zainal says:

Could you do one on cutting the cheese?

Ace Diamond says:

[Point 1] Why not (with Blue, Red, Green) just have blue cut a slice, then give red the option to take that slice, or give it to blue.  Then, of course the other of red/blue who didn't get the slice, does the 2-person procedure with green on the remainder of the cake?  It would work just the same, right?  Only thing I can think of is that you're letting more people optionally cut it, just to pare it down to a perfect third, in case the first guy didn't do well enough at cutting an accurate third; but it would seem that we're assuming perfect cutters, or else the 2-person method isn't quite fair.  Besides, if it's just about getting more accuracy, why not say that green can cut it too if he likes, and pass it back to blue, looping around to the beginning and continuing ad infinitum until it's perfect?  I may be missing something, but I don't see why you couldn't just go down the list of people in order, 1-on-1 matchup of cut+(accept/defer).  [Point 2] Blue and red could form a written pact.  Blue cuts a tiny sliver out of the cake, but insists that the giant portion is the "piece" he actually cut.  Red says, "Hell no, I don't want that giant piece, you keep it blue."  Red and green split the sliver, then Blue and Red split the giant piece per contractual obligation.  Blue and red each end up with essentially 50% of the cake, green with essentially 0%.

Felix Bade says:

A simpler n people solution: one person cuts the cake into n pieces. The cutter chooses last. Thus the cutter wants to make the smallest piece as big as possible eg. all pieces the same size.

Cam Whitling says:

TL;DR
Divide cake so everyone gets 1/n amount of cake (n = number of people)

kirkelicious says:

Substitute "cake" with "weed" and you have a practical application.

darkgtprince says:

so basically if you have n people, you cut the cake into 1/n pieces to share evenly

Harrison Harris says:

Adding the "I cut you choose" just complicates the last step, last diminisher works for 2 people as well.

Write a comment