Bert - converting to decimal and back was the long-winded way, and we didn't have calculators, so it was also inaccurate.

The first calculator I used for serious calculations was a Facit hand cranked rotary machine, with three sets of numbers. Worked to 15 digits, and accurate to better than 12. I could work out the mean and standard deviation of a set of 24 results on that quicker than using log tables.

As a site engineer in the 60s, needing to calculate areas and volumes with dimensions in feet and inches, I simply used duodecimal multiplication, writing X and L for 10 and 11 decimal - so 10 was 12. It wasn't difficult - we all learnt multiplication tables up to 12 times.

Phil