Here is a nice short easy puzzle.
Ten thieves have just made off with 56 identical rare gemstones. They realize that it is impossible for each thief to receive an equal number of the gems, but as it turns out, there are just enough senior thieves so that each of them can get exactly one more of the gems than each of the junior thieves. How many senior thieves were there, and how many gems did each thief get?
The Riddle of Scheherazade: And Other Amazing Puzzles by Raymond Smullyan.