Open thread, 25-31 August 2014

jaime2000

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4. Open Threads should start on Monday, and end on Sunday.

Previous open thread

If it's worth saying, but not worth its own post (even in Discussion), then it goes here.

Notes for future OT posters:

1. Please add the 'open_thread' tag.

2. Check if there is an active Open Thread before posting a new one.

3. Open Threads should be posted in Discussion, and not Main.

4. Open Threads should start on Monday, and end on Sunday.

KnaveOfAllTrades's idea of learning demographic & economic (GDP and its component parts) statistics of various places has occurred to me as a candidate for a useful Anki deck, so I second that.

Knowing some mathematical constants to a few significant figures can be useful. Memorizing √10 = 3.16 lets you interpret midpoints between ticks on a logarithmic scale, and √2 & √3 are the lengths of diagonals of unit squares & cubes. And knowing all three roots makes it easier to guesstimate square roots in general, using the √(ab) = (√a)(√b) result for non-negative a & b. Likewise for e.g. exp(2), exp(3), ln 2 & ln 3. The 68-95-99.7 rule should go on the list as well.