Wrong, But Useful: Episode 41


This month on Wrong, But Useful, @reflectivemaths and @icecolbeveridge are joined by @evelynjlamb, who is Evelyn Lamb in real life. She writes the Roots Of Unity column for Scientific American.

We discuss:

  • How Evelyn got into maths, into writing and into France
  • Evelyn picks the numbers of the podcast: 339,613 and 339,631, both of which are prime. Evelyn recommends @_primes_ (which are prime numbers in real life) We discuss what makes numbers nice and the gods of Tetris and prime numbers.
  • One of Dave’s students has spotted a nice pattern to do with squaring numbers comprising only 3s, only 6s or only 9s.
  • Our own personal Green’s theorems
  • Apparently the USA has a new president. Good luck with that. Evelyn’s article on the fall of Göttingen.1. Colin mentions an episode of This American Life and a big data article about the election; Evelyn points to a rebuttal by @mathbabe (Cathy O’Neil).
  • Colin does some mischievous Benford’s law analysis of the US election. (He says there are ‘about 100’ counties in Michigan; there are 83.)
  • Evelyn has been quaternion-hunting in Dublin! It has weather! And queues!
  • She has been playing Euclidea, which reminds Colin of Euclid, The Game.
  • Dave has a surprising number of balls, and has also been playing with Areamaze.
  • Colin stumbled on a neat right-angled triangle area expression: $A = \left(\frac{h}{2}\right)^2 \sin(2\theta)$, where $\theta$ is either of the acute angles.
  • Dave dresses as a protractor. Colin wants radian protractors. Dave wants fewer set squares and more circular protractors. Colin describes the centre of rotation thing, which works really well on a podcast. Dave points out that accurate drawing is regressive. Evelyn has never seen one! She has used a virtual protractor recently.
  • Farewells to Hans Rosling, Raymond Smullyan and Sir Peter Mansfield.
  • Nobody answered Dave’s puzzles, so no gold stars for loyal listeners this month.
  • Evelyn tops Dave’s terrible joke. And Colin’s, come to think of it.
  • This month’s puzzle2: roll six dice and remove any that show a six. Roll any remaining dice again and remove any that show a six. Roll any remaining dice a third time and remove any sixes. You win if you remove all of the dice or none of them. What are your odds of winning? (Thanks to Fred for the puzzle.)
  • Many thanks to Evelyn for being our special


    Colin is a Weymouth maths tutor, author of several Maths For Dummies books and A-level maths guides. He started Flying Colours Maths in 2008. He lives with an espresso pot and nothing to prove.

    1. I note she doesn’t get grief for plugging her work! []
    2. I’m aware of the inconsistency of paying to win a free drink. []


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