A researcher is experimenting with several regression equations. Unknown to him, all of his formulations are in fact worthless, but nonetheless there is a 5 per cent chance that each regression will-by the luck of the draw-appear to come up with `significant’ results. Call such an event a `success’. If the researcher tries 10 equations, what is the probability that he has exactly one success? What is the probability of at least one success?

Source: a gmat preparing forum.