Li Shenron said:
If they like more logical than poetry riddles, here's one I like very much.
Five greedy and bloodthirsty pirates found a treasure of 1000 pearls. From the one of lowest rank up to the chieftain, each pirate will make a suggestion about how to split the treasure: if the suggestion is accepted by majority, that's how the treasure it split, otherwise he'll be thrown to feed the sharks, and the next pirate will make his suggestion.
What must the first pirate suggest?
Let's see.
Assuming the pirates are smart and the proposing pirate has a vote...
I'll put my solution in a spoiler block if someone else wants to try it himself.[sblock]If the number of pirates is reduced to two, there can be no majority unless both remaining pirates agree, but the chieftain will probably simply murder the other guy so he can keep all the booty.
At this stage, the chieftain gets everything. Since he's a greedy and bloodthirsty pirate, this would be the optimal outcome for him.
However, the other pirates know that too, so the second-highest will cut a deal with the third-highest if only the three of them are left.
At this stage, the second-highest must accept just about any deal proposed to him as he will die next and get nothing if he doesn't. Let's give him 1 pearl.
The chieftain will get nothing here, as his vote is not required.
The chieftain will realize that he will end up with nothing if their number is reduced to 3, so his vote is easy to buy at the point where 4 of them are left. As long as he gets anything at all, he should be in favor. 1 pearl for him.
Together with the fourth-highest, who will propose the plan at this stage, that's two votes out of four.
The second-highest will not want things to proceed beyond this stage either, as he'll be forced to accept any deal at the next stage. Thus, he can be bought cheaply too, say, for 2 pearls - 'cause if things go on, he can only get a lesser deal.
This solution is of course not good for the fifth-highest pirate, who will be dead if things proceed to this point, nor to the third-highest, who will end up with nothing.
Thus, offering the third-highest 1 pearl at the very beginning ensures the fifth-highest his vote.
Giving the chieftain 2 pearls ensures his vote as well, as he will otherwise gain less. This is a majority (3-2).
The rest goes to the fifth-highest pirate.[/sblock]