Uploaded December 2025 | Updated September 2026, 2 weeks ago
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A man found a lost black wallet in Finland, he wrote a note and left it there for the wallet's owner to find. On this note he asked the wallet owner to plug his birthdate into an equation to get the man's phone number so he could call and arrange a recovery of the wallet. But how secure is this code? There would seemingly be many possible birthdates a malicious actor could try plugging in to find the man's phone number - but with a bit of thought, the number of possibilities can be significantly reduced. #viralmaths #maths #mathpuzzle
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Calculus: amzn.to/3PieD1M
Proofs and Set Theory: amzn.to/367VBXP (available for free online)
Statistics: amzn.to/4d5HbUQ
Discrete Math: amzn.to/3qfhoUn
Number Theory: amzn.to/3JqpOQd
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SOURCES
en.wikipedia.org/wiki/Telephone_numbers_in_Finland#Mobile_numbers
yle.fi/a/3-8074149
statista.com/statistics/1448352/mobile-payments-adoption-in-pos-in-finland
reddit.com/r/mildlyinteresting/comments/1jnxnfg/i_found_a_wallet_on_a_saturday_i_left_a_note_in_a
newsweek.com/stranger-finds-lost-wallet-returns-owner-viral-reddit-2053788
people.com/man-creates-clever-equation-to-return-strangers-lost-wallet-reddit-11708630
https://techbreak.com.br/went-viral-man-creates-secret-code-to-find-the-true-owner-of-a-wallet-found-on-the-street
nypost.com/2025/03/31/lifestyle/good-samaritan-devises-ingenious-hack-to-ensure-lost-wallet-finds-its-rightful-owner
0:00 Intro
2:00 Questions Answered
4:04 Revising the Odds
8:21 Applying Single Digit Rule
11:56 Finland Mobile Numbers
14:37 What Happened?
14:59 Mathshion
π Check out my math fashion brand! mathshion.com
β€οΈ Join the channel to get exclusive and early videos, original music, math lectures, and more!
youtube.com/channel/UCyEKvaxi8mt9FMc62MHcliw/join
A man found a lost black wallet in Finland, he wrote a note and left it there for the wallet's owner to find. On this note he asked the wallet owner to plug his birthdate into an equation to get the man's phone number so he could call and arrange a recovery of the wallet. But how secure is this code? There would seemingly be many possible birthdates a malicious actor could try plugging in to find the man's phone number - but with a bit of thought, the number of possibilities can be significantly reduced. #viralmaths #maths #mathpuzzle
More Math Chats: youtube.com/playlist?list=PLztBpqftvzxXQDmPmSOwXSU9vOHgty1RO
Business Inquiries: wrathofmathlessons@gmail.com
Textbooks I Like!
Graph Theory: amzn.to/3JHQtZj
Real Analysis: amzn.to/3CMdgjI
Abstract Algebra: amzn.to/3IjoZaO
Linear Algebra: amzn.to/43xAWEz
Calculus: amzn.to/3PieD1M
Proofs and Set Theory: amzn.to/367VBXP (available for free online)
Statistics: amzn.to/4d5HbUQ
Discrete Math: amzn.to/3qfhoUn
Number Theory: amzn.to/3JqpOQd
Outro music: youtube.com/shorts/tfifiSdTZRg
Follow Wrath of Math on...
β Instagram: instagram.com/wrathofmathedu
β TikTok: tiktok.com/@wrathofmathedu
β X: https://x.com/wrathofmathedu
SOURCES
en.wikipedia.org/wiki/Telephone_numbers_in_Finland#Mobile_numbers
yle.fi/a/3-8074149
statista.com/statistics/1448352/mobile-payments-adoption-in-pos-in-finland
reddit.com/r/mildlyinteresting/comments/1jnxnfg/i_found_a_wallet_on_a_saturday_i_left_a_note_in_a
newsweek.com/stranger-finds-lost-wallet-returns-owner-viral-reddit-2053788
people.com/man-creates-clever-equation-to-return-strangers-lost-wallet-reddit-11708630
https://techbreak.com.br/went-viral-man-creates-secret-code-to-find-the-true-owner-of-a-wallet-found-on-the-street
nypost.com/2025/03/31/lifestyle/good-samaritan-devises-ingenious-hack-to-ensure-lost-wallet-finds-its-rightful-owner
0:00 Intro
2:00 Questions Answered
4:04 Revising the Odds
8:21 Applying Single Digit Rule
11:56 Finland Mobile Numbers
14:37 What Happened?
14:59 Mathshion
