3 people (pirates, if you read the same book I did!) get a room at an Inn and each pay $10. The Inn Keeper realizes the room was only $25 and that he overcharged them. He tells the clerk to give $5 back to the people. Seeing that the people wouldn't be able split the change evenly, and given that they weren't expecting the money back any way, the clerk pockets $2 and gives the 3 people $3.
Each receives $1 back, and one says: sweet! we got the room for $27 (3 x $9). The clerk still has $2 in his pocket.
The room was $27. The clerk has $2. That's $29.
Where's the missing $1?
Missing dollar puzzles like these have had a damaging effect on me for the past 40 years! Damn them! This same puzzle messed with my mind at an younger age. And so to this day, I can't produce a math or logic solution without second and triple-guessing myself! Doesn't matter if I arrive at the correct solution in the first couple of seconds, nor if the answer is staring me right in the face, I still re-examine my answer with an air of self-doubt... all because of this stupid puzzle that shattered my confidence all those years ago!