Why do people keep getting this wrong‽
Why Hacker News recommends it
HN links it to explain why people repeatedly get large-number arithmetic wrong in discussions of money and mental math.
What it is
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.
Recommended by 1 HN commenters across 1 different months, 2020 to 2025.
What Hacker News said
Recommends christiangenco · 2022-02 · on “What use is mental math in 2022?”
This mistake is so interesting to me. Here's a great explanation of what's probably happening: [this 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.
Cites infogulch · 2020-04 · on “Fed should pay every American, let hedge funds and billionaires ‘get wiped out’”
Matt Parker made a video that tries to explain how people keep getting this basic arithmetic completely wrong. [this video]
Cites TRiG_Ireland · 2023-10 · on “Edinburgh couple are handed £17K bill by Tesla as they 'drove in rain'”
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: [this video] .
Cites csours · 2025-01 · on “Very Wrong Math”
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.” [this video]