On the topic of conversion between Imperial and SI units of length there is a well known method of
quickly converting aliquot parts of an inch to millimetres using the approximation 254 = 256
If you have a fractional inch dimension, multiply top and bottom of the fraction by two repeatedly
the denominator equals 256.? Shift the decimal point of top and bottom one place to the left.? The
numerator now equals the inch dimension times 25.6, which is the equivalent number of millimetres
(to less than 1% error)
Darn, that is a neat trick. I really like simple numerical methods like that.