And there was I learning them up to 15.

Richard's Why is is socially acceptable to admit to being innumerate, but not to being illiterate? has been a longstanding question for me.

Like other posters here I learned on Lsd, tons, cwt, lbs & ozs etc and used the various tricks above but that was in the days BC; before calculators. Newport Boy mentioned the hand operated Facit; I never even saw one of these until I got to uni and recently inherited one that (apparently) was a war trophy from an uncle. By the time I got to uni there were electric rotary Facits and we preferred them but my supervisor could make the hand cranked one work faster than the electric ones.

The onset of cheap electronic calculators (my first HP was a week's pay) has allowed the mental arithmetic muscles to remain flabbily unused and mathematical tables and slide rules are relegated to museum displays, so our constant use of them, driving observable patterns and links between numbers and concepts into our consciousness, doesn't occur with current students. When they work checkout shifts their employers require them to rely on the electronic displays so they don't get much in the way of reinforcement that we did. So much for inability with arithmetic!

Then there's the university mathematical establishment. There are brillliant exceptions, but I've lost count of those who regard mathematical ability to be "so far above the common herd" and wish to retain their status as "members of a special club restricted to only those with superior qualifications." These people behave as though any lowering of the drawbridge, by teaching well enough for intelligent students to grasp and develop mathemetical concepts, will decrease their own special status. Fortunately, "real" mathematicians are better than that.

And, while most of us write and thus take an actively participatory role in literature, even if the writing isn't much more complex than emails, not many of us take a similarly active and participatory role in mathematics beyond basic arithmetic. Even when maths concepts are on display all around us in our daily routines.

Rant over! I feel better now.

Cheers, Rowan