[eadmund]

Even worse, people who say ‘3 times less than’ (which would be n - 3n = -2n) when they mean ‘one third as much as.’

And of course, the worst people of all think that one third is less than one fourth.

Personally, I blame the widespread usage of decimal notation rather than fractions. The so-called ‘metric’ system (a misnomer, because every system of measurements … measures) bears a lot of blame here.