When I was training for surveying exams, the new metric system was introduced to replace the imperial system, in the late sixties.
We all had to ditch the old Standard Method of Measurement, and use millimeters etc. It was chaotic, and the tutors were none the wiser as well, especially in the earlier months. There was continued debate as to whether one measured in millimeters or centimeters, and how many noughts one wrote after the decimal point. Up to then, measurements were quantified by multiplying feet and inches using duodecimals, and this was all before calculators came on the scene as well! Many's the time I would arrive at the office, (very junior back then), and have to calculate squares and cubes all day, on scrap paper...
When I moved to London to work, the firm had just bought two desktop calculators, which were the size of a typewriter, and cost the same as a Mini Minor!
The calculator I have in front of me cost three quid on Ebay, and is the size of an old Gold Leaf fag packet...