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Why do people keep getting this wrong‽

Stand-up Maths · 2M views · 2020-03-24 · 12:49

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Overview

Matt Parker of Stand-up Maths explains why people keep making the same mistake with millions and billions, using a Bloomberg cash calculator example. He looks at the unit slip behind the repeated arithmetic error.

On Hacker News

HN links it to explain why people repeatedly get large-number arithmetic wrong in discussions of money and mental math.

Recommended by 1 HN people across 1 months · HN mentions 2020–2025

Topics

Recreational & visual mathMath & theory (other)
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mathematicsmillions and billionsmental mathnumeracymatt parker

What people said

christiangenco · 2022-02 · Recommendation

This mistake is so interesting to me. Here's a great explanation of what's probably happening: [VIDEO] tl;dr: mentally we take off "millions" as a unit, do the calculation, then add "millions" back on. This works for addition, subtraction, and inequality but fails for multiplication and division.

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csours · 2025-01 · Reference

Reminds me of this classic: [LINK] “Bloomberg spent $500 million on ads. The U.S. population is 327 million. He could have given each American $1 million and still have money left over.” [VIDEO]

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TRiG_Ireland · 2023-10 · Reference

I'm not sure that there's a name for that kind of maths error, but there is a reason why people keep making it, as Matt Parker discusses: [VIDEO] .

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Sources

Video by Stand-up Maths, played through YouTube.

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