Spot the Frippet: flap.

Letter go into flaps, and in Britain the vast majority of thses flaps will be set into a front door:


photo by Timo Newton-Syms https://www.flickr.com/people/19935963@N00

but do mathematicians ever go into flaps? 

See the puzzle, below, and see of you can work it out calmly!

In the meantime, tents have flaps:


photo by Paritosh chaudhary

and so do envelopes, pockets, and aeroplane wings:


photo by David Monniaux

And then there are flapjacks*. In the USA Canada and New Zealand (my Collins dictionary tells me) a flapjack is a pancake, and in this case the flap in flapjack is understandable because you have to flap the pan to turn the flapjack over. In Britain, however, a flapjack is a chewy dense cake made with porridge oats and golden syrup, and, far from flapping it about, you press it firmly into the pan to make sure it sticks together while it's being baked:


photo by sk8geek https://www.flickr.com/photos/sk8geek/

So where the flap has come from in that case is a puzzle: though not the only one (see below). 

Spot the Frippet: flap. This word is first recorded in the 1300s and is probably an imitation of the action of flapping.

The mathematical flapjack puzzle. My flapjack recipe (and this is true) calls for an eight inch square baking tray, but instructs the baker to mark out the soft newly-baked cake mixture into twelve squares.

Can you work out how this can be done?

It is possible - though I don't think the result is what the writer of the recipe had in mind.

*The jack is basically a word meaning man, or thingie-that-does-something, and comes from the shortened form of the name John.