Sorry, this is wrong. Requiett already had it right.ayanefan wrote:If we deduce that only 1 sign is true, then we have to say that the treasure is in the 3rd cave. This because it's impossible to have both signs 1 and 2 to be true if 3 contradicts them. If we assume that sign 3 is true, then it is true that caves 1 and 2 are false. Therefore, using XOR, cave three has the treasure.
"If we assume that sign 3 is true, then it is true that caves 1 and 2 are false."
If you assume that sign 3 is true, and making 1 and 2 false, 1 would mean that the treasure isn't there, and 2 would mean that it IS there, therefore 3 would be false.
Basically, 1 and 3 can't have it because they both imply that the treasure is inside them, and since the old man said AT MOST one is true, it also implies that none of them HAVE to be true. Therefore, since none of them are true, cave 2 would be the only one not to contradict any of the other caves and has the treasure. (yes, I'm just re-stating what Req had already stated, but maybe you didn't understand what he was saying)
