The latest stupidity comes from a furniture store. They're boasting that "some items have been reduced to half price, then a further 10% off".
For example, an £899 item reduced to £299 (I'll call the figures £900 and £300, just to make the rest of this easier). Errr, run that by me again ? Neither of the two possible interpretations of their blurb gives 300 from 900. It's not 50+10 = 60% off, because that would be £360. It's not 10% of the halved price, either, because that would give £405.
It isn't just a typo in one item, either, it was the same sort of reduction on every item (e.g. £1199 to £399).
Gah ! Stupid advertising people ! Why couldn't they just say "two-thirds off" or "reduced to one-third of their original price" in the first place !
(ok, that's my exclamation point quota used up for the rest of the month. I'm calm now ... )