In this month’s Christmassy episode of Wrong, But Useful, @reflectivemaths and I discuss:

  • Number of the podcast: 9Number 9. Number 9.
  • Shout outs to:
    • @aap03102 (Chris Smith) for his maths newsletter
    • @mathistopheles (Thomas Oléron Evans) and @fryrsquared (Hannah Fry) for sending me a copy of their book
    • @chalkdustmag for the lovely card
  • @fryrsquared - The Joy of Data on BBC four
  • Mathematics exhibition at the Science Museum
  • “Did you know that the incircle of a 3-4-5 triangle has radius 1?”
  • (Via @arithmaticks): owt to the nowt = 1
  • Class “Girls were better than boys by 1”
  • (Via @danicquinn): How would you do 12.5 x 140 ?
  • (Via @christianp): suppose you want students to round -2.3. You round it to the nearest…?
  • New GCSE mocks
  • @jamesgrimes’s personalised video for Dave and his classes and his MathsJam talk
  • Puzzles:
    • From Ep 37: 2, 3 and 7 are the three numbers whose reciprocals don’t reach 1, but get as close as possible. Gold stars to @fenneklyra, @chrishazell72, @dragon_dodo, and @aap03102
    • From Ep 38: Another gold star to @FennekLyra for solving the 100! Puzzle, which we won’t give away the answer to.
    • How many gifts are there, in total, in the Twelve Days of Christmas? And what do you end up with most of? What if there were 24 days of Christmas?