The question as it appears in the 06/05 edition of Specs & Techs from GlobalSpec:
Tom meets his old math teacher John.
"Hello John, how old are your three children now?"
"Well, if you multiply their ages together you get 36, and, if you add their ages you get the number on that bus."
Tom is perplexed, so after a while John adds, "Oh! And the oldest plays the piano," at which point Tom is happy.
How old are the three children? What number is on the bus?
Thanks to Randall who submitted the original question.
(Update: June 12, 8:39 AM EST) And the Answer is...
The trick is in realising that the first two bits of information are not quite enough for Tom to arrive at a unique solution. The final snippet (somewhat obliquely) resolves his dilemma.
There are only eight possible combinations of ages which when multiplied together give 36.
1, 1, 36 (sum 38)
1, 2, 18 (sum 21)
1, 3, 12 (sum 16)
1, 4, 9 (sum 14)
1, 6, 6 (sum 13)
2, 2, 9 (sum 13)
2, 3, 6 (sum 11)
3, 3, 4 (sum 10)
If the number on the bus had been anything other than 13 then Tom would have known immediately how old all the children were. Of the two possibilities which add up to 13 only the answer [2, 2, 9] has an "oldest" child, and, this is therefore the answer.
Congrats to ve9gfi for beign the first to correctly answer the puzzle.

Re: My Teachers Three Kids: Newsletter Challenge (06/05/07)