Cambridge Mathematical Tables
Before mathematical calculators there were slide rulers and before slide rulers there were mathematical tables.
School children at secondary school used these table – it involves looking up values and adding or subtracting numbers. These are of course done instantly on modern calculators – but it was all subtracting and adding numbers, looking up tables and finding a result. Every student was issued with a book of tables. Even when the first calculators were introduced, they were so expensive (and by today’s standards very primitive) that mathematical tables were used.
Shop keepers didn’t have electronic cash registers and used “ready reckoners” - a book that listed all the combinations of prices and quantity a shop keeper could ever come across. (e.g. 23 items at one pound eighteen shillings and six pence each.)