The everyday usefulness of mathematics

Metafilter recently had a discussion of mathematics as applied to moving -- the neatest thread I've ever seen there. I am reminded of the story told by Ralph Boas about a mathematician who, watching movers try in vain to manoeuvre a large couch through a narrow doorway, sat down and worked out to his own satisfaction that it could not be done -- only to find, on returning to announce his accomplishment, that the job had been done already in his absence.