Wrong, But Useful: Episode 56


In Episode 56 of Wrong, But Useful, we’re joined by @zoelgriffiths (Zoe Griffiths), maths communicator from Think Maths.

  • Zoe had her poem e, to thee, x in @chalkdustmagazine recently, and did a set about misleading statistics at @aeoud (An Evening Of Unnecessary Detail)
  • Bad polls and fake stats, including this from the Mirror and a report on breast cancer screening, righteously rubbished by @dspiegel
  • Number of the podcast: 477277, a prime that would probably get you a taxi (and, indeed, would – if you were in Bolsover – thanks, @mathsjamPOR.)
  • Colin has upgraded his experience of G4G from “would probably go again” to “would definitely go again”.
  • The Aperiodical Wikiquote editathon went well:
  • Zoe gives RI Masterclasses on the lottery and has compiled stats about it.
  • Dave brings up the clocks in exam halls non-story.
  • Dave has spotted 24-hour analogue clocks.
  • It’s National Numeracy Day tomorrow (2018 May 16th)
  • Colin is reading Eli Maor’s e: The Story Of A Number and approves. He also writes books, such as Cracking Mathematics and The Maths Behind, in case you need to get your total up for free shipping or something.
  • Professor Yaffle was based on Bertrand Russell
  • @samhartburn’s husband 3D printed a 3D noughts-and-crosses game!
  • Zoe has been making a cricket cake.

    We discuss the shape and dimensions of a pitch. We discuss oblongs, geometrical and leafy, as well as discorectangles), degrees of parallelism and the Jastrow illusion.

  • Upside-down triangles and unhelpful conventions.
  • An email from Chris Warburton:

    I was catching up on Wrong But Useful, and had some thoughts on the discussion of maths in school in episode 51.
    The thing which always sticks in my mind about school maths was the word “simplify”, which cropped up everywhere but didn’t seem to have any consistent meaning. One question might ask to “simplify” x^2 + 8x + 15, expecting the answer (x + 5)(x + 3), whilst another might ask to “simplify” (x + 5)(x + 3) and expect the answer x^2 + 8x + 15 (or at least it seemed that way to me at the time).
    I get that questioners don’t want to give too much away (e.g. by saying “multiply out” or “factorise”), but as maths teachers/tutors do you know if the curriculum uses the word “simplify” to mean anything other than “rewrite this expression in some non-trivial way that you’ve been taught”?
    Tangentially, in computer science we often say ‘simplify’ as a synonym for ‘run’, when the expression is a piece of code. That works since the equations in a program are usually ‘directed’, e.g. “x + 0 = x” will cause occurrences of “+ 0” to be eliminated, but it doesn’t cause “+ 0” to get introduced anywhere. This makes “simplifying” unambiguous. In algebra the equations ‘go both ways’, so it’s ambiguous as to what “simplify” actually means.

  • (We think) Dave came across a game called Block Out.

    Players: 2
    Materials: 2 dice, graph paper, a colored pencil or crayon for each player, scratch paper (for totaling scores)
    Object: Cover the largest area by placing
    rectangles on graph paper
    How to Play: Alternate turns. On a turn, a player rolls
    two dice and draws a rectangle using the numbers rolled
    as the length and width on graph paper. For example, if
    the numbers rolled are 2 and 3, the player draws a 2 by 3
    Play continues until a player can’t place a rectangle. Both
    players add the areas of all of their rectangles, and the
    highest score wins.

  • @solvemymaths’s lovely puzzle went viral:
  • @christianp has made a web thing to express any positive integer as the sum of three palindromic integers
  • Puzzle feedback: Thanks to @MB_Whitworth for his lovely explanation of the last puzzle – the answer was 272.
  • Zoe’s question: If you multiply me by 2, subtract 1, and read the reverse the result you’ll find me. Which numbers can I be?


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.


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I teach in my home in Abbotsbury Road, Weymouth.

It's a 15-minute walk from Weymouth station, and it's on bus routes 3, 8 and X53. On-road parking is available nearby.