Controversial Math Problem - The Real Answer Explained

This problem has gone viral recently. But its story begins 10 years ago when a government banned it from schools. I explain how a student could actually solve it, and I explain how you can find all solutions in just a few lines of code. 0:00 problem 2:33 history 6:51 setup 8:52 solution 1 13:04 solution 2 15:32 family 17:50 mistake 20:49 correct code 22:15 fractions Thanks to @scottwestleysmith3196 who alerted me of typos in the original video. I have cut 15 seconds around 20:32 to cut out this mistake, so beware of a rough transition cut in the video. Origin https://tuoitre.vn/nguon-goc-bai-toan-lop-3-gay-sot-751485.htm https://news.tuoitre.vn/meet-the-vietnamese-teacher-who-challenged-third-graders-with-brain-mangling-math-puzzle-1035201.htm http://vnexpress.net/tin-tuc/giao-duc/bai-toan-lop-3-lam-kho-ca-tien-si-3220186.html https://www.theguardian.com/science/alexs-adventures-in-numberland/2015/may/20/can-you-do-the-maths-puzzle-for-vietnamese-eight-year-olds-that-has-stumped-parents-and-teachers https://tuoitre.vn/chi-mong-cac-em-hoc-tot-751707.htm https://tinmoi.vn/amp/so-gd-dt-dong-y-nhac-nho-nguoi-ra-bai-toan-lop-3-lam-kho-ca-tien-si-011360294.html https://tuoitre.vn/vu-bai-toan-lop-3-gay-sot-so-gddt-lam-dong-xu-ly-nhac-nho-cac-co-giao-truong-th-thang-long-753081.htm https://dantri.com.vn/giao-duc/go-bo-thay-the-bai-toan-lop-3-khien-bao-anh-dau-dau-1433288116.htm https://www.reddit.com/r/math/comments/36gdac/a_challenge_for_3rd_grade_kids_in_vietnam_please/ https://lazi.vn/edu/exercise/44114/hay-dien-cac-so-tu-1-den-9-vao-o-trong-de-duoc-ket-qua-da-cho https://lifestyle.znews.vn/sao-lai-nhac-nho-co-giao-vu-bai-toan-lop-3-gay-sot-post543550.html 3rd grade book https://nhasachquangloi.vn/phieu-bai-tap-cuoi-tuan-toan-va-tieng-viet-3.html 2015 CC BY 4.0 https://commons.wikimedia.org/wiki/File:Apple_Watch_Sport.jpg My 2015 video https://www.youtube.com/watch?v=WiB2_dXSSMg askmath https://www.reddit.com/r/askmath/comments/1o3qobr/how_to_solve_this_cross_math/ wrath math video https://www.youtube.com/watch?v=1aywN5eFOys permutation function https://code.activestate.com/recipes/126037-getting-nth-permutation-of-a-sequence/ Python online https://www.online-python.com/ Members get early access to videos YouTube members https://www.youtube.com/channel/UCHnj59g7jezwTy5GeL8EA_g/join Patreon members https://www.patreon.com/mindyourdecisions Support the channel with a one-time donation https://www.paypal.com/donate/?hosted_button_id=REZRY3QRQPYQA Subscribe: https://www.youtube.com/user/MindYourDecisions?sub_confirmation=1 Send me suggestions by email (address at end of many videos). I may not reply but I do consider all ideas! If you purchase through these links, I may be compensated for purchases made on Amazon. As an Amazon Associate I earn from qualifying purchases. This does not affect the price you pay. Book ratings are from January 2025. My Books (worldwide links) https://mindyourdecisions.com/blog/my-books/#worldwide My Books (US links) Mind Your Decisions: Five Book Compilation https://amzn.to/2pbJ4wR A collection of 5 books: "The Joy of Game Theory" rated 4.2/5 stars on 564 reviews http://amzn.to/1uQvA20 "The Irrationality Illusion: How To Make Smart Decisions And Overcome Bias" rated 4.2/5 stars on 55 reviews http://amzn.to/1o3FaAg "40 Paradoxes in Logic, Probability, and Game Theory" rated 4.2/5 stars on 81 reviews http://amzn.to/1LOCI4U "The Best Mental Math Tricks" rated 4.3/5 stars on 148 reviews http://amzn.to/18maAdo "Multiply Numbers By Drawing Lines" rated 4.5/5 stars on 57 reviews http://amzn.to/XRm7M4 Mind Your Puzzles: Collection Of Volumes 1 To 3 https://amzn.to/2mMdrJr A collection of 3 books: "Math Puzzles Volume 1" rated 4.4/5 stars on 138 reviews http://amzn.to/1GhUUSH "Math Puzzles Volume 2" rated 4.2/5 stars on 45 reviews http://amzn.to/1NKbyCs "Math Puzzles Volume 3" rated 4.3/5 stars on 38 reviews http://amzn.to/1NKbGlp 2017 Shorty Awards Nominee. Mind Your Decisions was nominated in the STEM category (Science, Technology, Engineering, and Math) along with eventual winner Bill Nye; finalists Adam Savage, Dr. Sandra Lee, Simone Giertz, Tim Peake, Unbox Therapy; and other nominees Elon Musk, Gizmoslip, Hope Jahren, Life Noggin, and Nerdwriter. My Blog https://mindyourdecisions.com/blog/ Twitter https://twitter.com/preshtalwalkar Instagram https://www.instagram.com/preshtalwalkar/ Merch https://teespring.com/stores/mind-your-decisions Patreon https://www.patreon.com/mindyourdecisions Press https://mindyourdecisions.com/blog/press