Uploaded September 2025 | Updated September 2026, 2 weeks ago

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Recently a parent posted this second grade math problem about addition to r/HomeworkHelp. I had a great big laugh when I first read it, but when you actually think about this math problem it goes from hilarious to Vitruvian Man levels of historical precedence very quickly. Today we discuss the problem and the famous error which is its solution - the off by one error. #math #homeworkhelp

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SOURCES
reddit.com/r/HomeworkHelp/comments/1norruh/2nd_grade_math_how_do_you_answer_this
web.archive.org/web/20160305221341/http://www.dsm.fordham.edu/~moniot/Opinions/fencepost-error-history.shtml
betterexplained.com/articles/learning-how-to-count-avoiding-the-fencepost-problem

0:00 Intro
1:21 Here's the Deal
3:49 Fencepost
5:29 Vitruvius
9:23 Examples
12:51 Conclusion