Crusty’s Perfect Square
RAY: The number ends with two. And there are no perfect squares that end in two. It's impossible.
TOM: Impossible indeed.
RAY: Why? Because the units digit of any perfect square is determined by the units digit of its square root. Take the number one, for example, square it and you get one. Take the number two and square it, it comes out four. The number three comes out nine. But there is no number that you can square and get a two at the end. That's what Crusty knew. Do we have a winner?
TOM: The winner this week is R. D. Cook from Middleton, Wisconsin!
[ Car Talk Puzzler ]