logical fallacy

A racing car driver worried by the possibilities of a blowout consulted a mathematician.

"Don't worry," he was told, "there is only chance in a thousand of any one car blowing a tyre."

"But I do a hell of a lot of driving," he retorted.

"Then always carry a flat tyre yourself," replied the mathematician, "because there's only one chance in a million of a car having two flat tyres".