Sums

The humble calculator was revolutionary in its day and combined with the U.K. decision to adopt decimalisation of the currency made life much easier.

Unless you were old and many older people continued to use 'old money' when working out costs.

Pre-decimalisation 'sums' were hard work. E.G. In old money 2oz Sweets at 2/6 a lb works out at 3 penny, 1 half-penny & 1 farthing.

Before calculators people were good counters having to work it all out, mostly in their head. Now people can be employed at the sharp-end of financial transactions without needing to apply any mental arithmetic whatsoever.