takman, that’s a classic one. It’s beauty derives from the fact that once its realized that the guys paid 27$, the initial 30$ payment isn’t relevant anymore. The split should be:
27$ (guys) = 25$ (old lady) + 2$ (girl). Again, the 30$ doesn’t belong here anymore.
Now about the original riddle (takman & Bedz): One should assume that the stranger was telling the truth, otherwise it would have been your trivial solution indeed. This is really yet another one of the math induction problems; It’s based on the fact that you know something, but you don’t know what the others know, and that’s what’s keeping the balance of terror intact. Once someone adds new information, not to what you know, but to you know OTHERS know, he really starts a chain reaction, taking over the whole set.
D.
If you caught the drift of the original one, here’s another one for you:
Let’s say you have another village wholly populated by married couples. Whenever a wife cheats on her husband, she does it with all the village men. Now, the moment the husband figures it out, he can shoot her in the head the next morning (cool place to live isn’t it). As in the previous riddle, they never discuss it. One evening, that old stranger comes to the village, gathers the men, and tells them that there are cheating wives in the village. Ten nights pass, and in the morning after, husbands start shooting their wives.
1st question - why? 2nd question - how many of them?
Shouldn’t be too hard for you if you caught the first riddle’s drift.
D.