Re: [math-fun] car talk puzzler

I wrote:

There is an exactly isomorphic puzzle in Martin Gardner's book "Puzzles from other worlds", collected from a column he ran in Isaac Asimov's Science Fiction Magazine.

Er, except that the exact way the question is asked there is different and if you read Gardner's version of the puzzle it may give away a key part of the answer to the Car Talk one. So if you have that book but no recollection of the puzzle and want to solve it afresh, best do it before comparing. -- g