Thursday, July 15

My fav Puzzle

The Thirteen Wells There is an island with thirteen wells, all of which have poisoned water. The wells are labelled 1-13. All the poisons taste the same, like regular well water. If someone/something drinks a cup of poison from well X, they will die unless they drink another cup of poison from a well numbered greater than X (within a reasonable amount of time). For example, if I drink from well 4, I will die unless I have a cup of poison from well 5 or well 6 or well 7, etc. So... there is a dragon and a knight on this island. They are both rational thinkers. Only the dragon, however, can reach well #13 because it is too high for the knight to get to. Both the knight and the dragon get a cup of water from one of the wells (without the other seeing) and exchange cups, and they have to drink it. Amazingly, the dragon dies and the knight lives. How did this happen?
Click on the Comments for the Answer :

2 comments:

Vc said...

Both the dragon and the knight know that the knight cannot reach well 13. The dragon therefore probably filled his cup from well 13 knowing that the knight could not get an antidote to the water from that well. The knight would have figured this out and so prepared himself with another cup of water from well 1. First he drinks water from well 1 (weakest poison) then he quickly drinks water from the dragon's glass. Then he quickly drinks well 1 again, and then he quickly drinks water from well 2. That way, if the dragon offered him water from wells 2-13 the knight simply poisoned and cured himself twice. If the dragon gave him water from well 1, then what actually happened was that he drank water from well 1, and then water from well 2 - which would save him. On the flip side, the knight gave the dragon a cup filled from the lake surrounding the island. The dragon, thinking he got a cup of poison from well 1 (or up to well 11), drank it and then immediately drank from well 13 and killed itself.

Anonymous said...

Aaaargh! I will never drink water anymore from any well. Pffffft.