# Do you understand this viral very good math movie clip? (Nathan solves math problem X+Y)

From Mathologer.

Recently one of you requested that I explain the math(s) in this clip which recently went viral.

https://youtu.be/mYAahN1G8Y8

It’s a clip taken from the movie X+Y aka A brilliant young mind. The math(s) problem that Nathan, the main character in this movie, is working on in this clip is a simplified version of the first part of a problem that was shortlisted for the 2009 International Mathematical Olympiad. Here is a link to the shortlist.

https://www.imo-official.org/problems/IMO2009SL.pdf

The problem in question is problem C1 (the number 50 in the problem has been replace by the number 2 in the clip). This problem was suggested to the makers of the movie by Lee Zhao one of the maths consultants of the movie. This Note that the file I’ve linked to ere also includes solutions.

This problem was invented by Michael Albert who is a mathematician and computer scientist working at the University of Otago in New Zealand.

https://en.wikipedia.org/wiki/Michael_H._Albert

The 4-colour puzzle that I am challenging you with at the end of this video was invented specifically for the movie X+Y by the U.K. mathematician Geoff Smith who was another math consultant for the movie.

https://en.wikipedia.org/wiki/Geoff_Smith_(mathematician)

Geoff Smith also served for many years as the leader of the United Kingdom team at the International Mathematical Olympiad and is the current president of the IMO board. He also appears in a cameo role in the movie. He is sitting next to Nathan’s mother in the corridor outside the hall in which the math(s) olympiad is taking place at the end of the movie.

https://imgur.com/a/cjWLHKi

Here is scan of the fictional IMO questions that the students dealing with at the end of the movie.

https://imgur.com/a/C1Uxkbd

Actually they adapted the first problem a little bit to make it fit in better with the story

https://imgur.com/a/9lP4zKe

These questions and their solutions also appear in the book by Geoff Smith, A Mathematical Olympiad Companion UK Mathematics Trust

https://www.ukmt.org.uk/product/95

Here is my presentation of an animated solution of the 4-color problem on Mathologer 2.

https://youtu.be/4uQfY8NSM6w

Please also check the description of that video for more information and the announcement of the winner(s) of the t-shirt.

Thank you very much to my colleague Norman Do for digging out all this info about the origins of these problems.

Marty and my MMDB (Mathematical Movie Data Base) lives here

https://www.qedcat.com/moviemath/

Here is the preview of Marty and my book Math goes to the movies on Google books (features a couple chapters)

https://tinyurl.com/f57wr72v

The music accompanying my Thank you at the end is I Promise by Ian Post (just like for the last video)

Enjoy!

Burkard

P.S.: Here is a great account featuring an ex IMO participant who contributed to the making of X+Y.

https://ncs6mathssociety.wordpress.com/2015/09/09/lee-zhou-zhao-visits-the-ncs/

His name is Lee Zhou Zhao. He also made a cameo appearance in the movie

https://imgur.com/a/uFwS8Yv