POUND CAKE
four equal weights — a recipe whose name is its ratio
DIVISIBILITY TESTS
what to read in a written number instead of dividing it: the tail, the digit sum and composite divisors
THE DOOMSDAY RULE
the weekday of any date in the Gregorian calendar, worked out in the head in three steps
THE RULE OF 72
the time it takes steady growth to double: the division you can do in your head, how far it misses and why the divisor is what it is
AMP MIC POSITIONS
where to place a mic in front of a guitar cab and how each spot sounds — after the Shure chart
UKULELE CHORDS
the first twelve chords · standard tuning G C E A
RED CABBAGE pH INDICATOR
the purple juice that changes colour: acid or base, without asking a book
IMPERIAL UNITS
convert in your head · without a calculator
APERTURE, SHUTTER, ISO
one stop is twice the light: three scales with the same step on each
THE RACING LINE
one corner, three apexes, the time computed
TYRE SIZE
what the sidewall marking is made of and what it works out to