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It's the (slightly delayed) monthly chat between @reflectivemaths (Dave Gale) and me on whatever maths has caught our eyes.

This month:

- Why protractors and set squares? You can find centres of rotation.
- Why constructions? Colin launches an impassioned defence and compares them to Killer Sudoku
- Dave has some great ideas for improving the Mathematical Instruments package, while Colin wants to shake up the calculator industry
- Exams: do you deserve full marks for a lucky guess? Neither of us think so, but the GCSE disagrees. Outrage ensues, before Dave suggests not ranting about exams yet again.
- Dave goes shopping for horse-balls but only finds confusingly-priced pizza [link]. We fail to discuss the density of prawns. Colin suggests the reason is 'economics'. Dave brushes this off. Dave is unhappy about the convention in some puzzles that A=1, B=2 and so on but Colin thinks he's being oversensitive.
- Stephen Hawking lets the side down with a Perfect Formula. Even for charity, even with some actual statistics behind it, that's a case for the Maths Police.
- Dave interrupts the football commentary with a super-relevant query: is half a million chickens a lot to rehome ?
- Colin's reading: Dead Reckoning by Ronald Doerfler, which has inspired him to try to do 1/97 in his head (it's 0.010309278350515463... - he could go on, but your calculator couldn't.)
- The World Cup seeding system: how England, Holland and Italy managed to fall foul of it by picking silly friendly opponents.
- Dave interrupts the football commentary again to explain that that last month's answer was $\frac{5}{11}$; gold stars to @srcav and @notonlyahatrack
- This month's World Cup puzzle:

How many possible World Cup tournaments are there? There are 32 teams in eight round-robin groups (each with six games, each of which has three possible results) and 16 knock-out games (each with two possible results). We're not interested in the actual number: just how many digits long it is.

- Colin doesn't understand Graham's Number and isn't really sure how to say 'Knuth'

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* Updated 2014-09-21 to fix a link.

## Colin

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.

## WrongButUseful

RT @icecolbeveridge: [FCM] Wrong, But Useful: Episode 15: http://t.co/gS5OGNwzBd

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