Like many children growing up in countries that still used the old British Pounds, Shillings and Pence (£sd) my early years in school was blighted by the dread exercise of reduction.
Basically, take a sum of money, break it down to the number of pennies or half pennies involved, all necessary, as unlike sensible decimal currency it was all completely non-intuitive.
Multiply the number of pound by 20 to get the number of shillings. Add on any extra shillings. Multiply the number of shillings by 12 to get the number of pennies and add on the extra pennies. Multiply by 2 to get the number of halfpennies. Later, as preparation for decimalisation, we then had to convert the resulting sum to the new currency – multiply by ⅚ to get the number of cents (a cent was worth 1.2d, hence the totally useless five cent coin is still the size of an old sixpence), and then move the decimal point to get the number of dollars and cents.
Tedious, boring and did wonders for being able to do mental arithmetic.
That of course has been in the box of dead useless knowledge until I started working on the project. Prices and materials were of course in £sd, and of course, as the old boy locked the door in 1968, 2 years after decimalisation, some of the prices are in both systems, eg 75c and 7/6, and of course there’s sometime a little creative rounding to document.
So I’ve good at pre decimal currency, surprisingly good, even though it’s still a useless skill in the main …