This is a famous problem that has been used in technical interviews, and it has even appeared on a Mathematical Olympiad. There are 4 good batteries and 4 bad batteries, and you need to insert 2 good batteries to make a flashlight work. How many tests do you need?
0:00 problem
1:53 estimate
5:18 strategy 1
7:47 strategy 2
10:46 solution
13:08 proof
Bogumił Kamiński
https://bkamins.github.io/julialang/2023/06/23/graphspuzzle.html
Brazil Olympiad
https://imomath.com/othercomp/Bra/BraMO05.pdf
StackExchange
https://math.stackexchange.com/questions/3323740/brazilian-math-olympiad-question-about-batteries-and-a-torch
https://math.stackexchange.com/questions/3115018/we-have-n-charged-and-n-uncharged-batteries-and-a-radio-which-needs-two-char
https://puzzling.stackexchange.com/questions/108023/flashlight-and-8-batteries
Mike Pawliuk
https://mikepawliuk.ca/2012/09/06/the-battery-problem-math-for-my-mom/
Glassdoor
https://www.glassdoor.com/Interview/Round-4-It-was-a-manager-round-Q1-Asked-me-to-explain-you-previous-employer-product-architecture-Q2-It-was-puzz-QTN_4674074.htm
LogicallyYours
https://www.youtube.com/watch?v=wOosTU73OCg
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.
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 2023.
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 4.3/5 stars on 290 reviews
http://amzn.to/1uQvA20
"The Irrationality Illusion: How To Make Smart Decisions And Overcome Bias" rated 4.1/5 stars on 33 reviews
http://amzn.to/1o3FaAg
"40 Paradoxes in Logic, Probability, and Game Theory" rated 4.2/5 stars on 54 reviews
http://amzn.to/1LOCI4U
"The Best Mental Math Tricks" rated 4.3/5 stars on 116 reviews
http://amzn.to/18maAdo
"Multiply Numbers By Drawing Lines" rated 4.4/5 stars on 37 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 112 reviews
http://amzn.to/1GhUUSH
"Math Puzzles Volume 2" rated 4.2/5 stars on 33 reviews
http://amzn.to/1NKbyCs
"Math Puzzles Volume 3" rated 4.2/5 stars on 29 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