# Dr Livingstone

Mayharm
Posers and Puzzles 23 Jun '04 21:53
1. Mayharm
23 Jun '04 21:53
For some reason, everywhere I post this people allways get it wrong. Lets see how you chess dudes handle it:

Dr. Livingstone is walking on a trail through the jungle on his way to study a fascinating tribe whose religion requires them to dedicate their lives to the telling the truth or telling lies.

On the way Dr. Livingstone is spotted by a hungry lion who gives chase. Further up the trail splits and there are two natives from the tribe who, upon seeing the lion, quickly scamper up some nearby trees. Dr. Livingstone, being a rather portly gentleman, has no chance of making it up into a tree and so must pick the shortest path to the tribe's village. Unfortunately his sense of direction, never that good at the best of times, has completely left him and he has no idea which path would get him there quick enough.

He has just enough time, and breath, to ask one question of the natives before the lion catches up with him.

What question does he ask to find the correct path?

MÅ¥HÅRM
2. 23 Jun '04 22:25
What your fellow guard would say it's the shortest path? Then go in the opposite. Is this right?
3. 23 Jun '04 22:29
Originally posted by m4no
What your fellow guard would say it's the shortest path? Then go in the opposite. Is this right?
Only if there's one liar AND one truth teller. So, it won't work. Hmmm... what about &quot;If I asked you to tell me the shortest path, what would you answer?&quot;.

But of course, the time I just spent thinking, the lion would have eaten me. Life's rude!
4. Mayharm
24 Jun '04 00:59
Originally posted by m4no
What your fellow guard would say it's the shortest path? Then go in the opposite. Is this right?
wrong.

MÅ¥HÅRM
5. bbarr
Chief Justice
24 Jun '04 01:18
Ask native A this question: &quot;If I asked native B if trail A is the quickest way to the village, would he answer 'yes'?&quot;. If the answer is 'no', take trail A. If the answer is 'yes' take trail B.
6. Nemesio
Ursulakantor
24 Jun '04 05:241 edit
The answer is simpler than that, bbarr. You would simply have to ask &quot;If I were to ask you if this is the correct path to take, would your answer be 'no?'&quot;

1) If he is a truth teller, and it were the correct road, he would reply &quot;No, (I would not say no&quotðŸ˜‰.

2) If he is a truth teller, and it were not the correct road, he would answer truthfully &quot;Yes, (I would not say no).&quot;

3) If he is a liar, and it were the correct road, he would reply &quot;No&quot; to the question posed above (that is, the same as the truth teller). Why? Because if he were asked directly &quot;Is this correct path?&quot; he would say &quot;No (it is not),&quot; lying. However if asked would you answer &quot;no&quot; (the answer to which is yes) he must lie and say that he would not say no (lying about a lie).

4) If he is a liar, and were the incorrect road, he would reply &quot;Yes.&quot; Why? Because if he were asked directly &quot;Is this the correct path&quot; he would reply &quot;Yes (it is),&quot; lying. But, again, he must lie about lying; he must say &quot;Yes, (I would say 'no'ðŸ˜‰&quot; precisely because he wouldn't say &quot;no.&quot;

Perhaps this isn't simpler, but I think this is the correct question. Your question would be if there were two natives there &quot;If I asked your buddy here...etc. etc.&quot;

Just a thought.

Nemesio
7. Mayharm
24 Jun '04 10:59
Originally posted by nemesio
The answer is simpler than that, bbarr. You would simply have to ask "If I were to ask you if this is the correct path to take, would your answer be 'no?'"

1) If he is a truth teller, and it were the correct road, he would reply "No, (I would not say no"ðŸ˜‰.

2) If he is a truth teller, and it were not the correct road, he would answer truthfully ...[text shortened]... were two natives there "If I asked your buddy here...etc. etc."

Just a thought.

Nemesio
Very nice.

I've only seen this answer once before, it works just as well but wasn't the one I was looking for when I made the riddle.

It's not intended to be misleading that there are two natives...it's just that most are misled ðŸ˜‰

MÅ¥HÅRM
8. Nemesio
Ursulakantor
24 Jun '04 14:522 edits
You could ask a variant of bbarr's answer or something similar to m4no's answer, something like, &quot;If I were to ask a member of the other tribe, 'Is this the correct road,' would he say 'yes?'&quot;

Then do the opposite of what he says (the truth teller would tell the truth about the liar, or the liar would lie about the truth).

Is this what you were looking for?

Nemesio
9. Mayharm
25 Jun '04 13:22
Originally posted by nemesio
You could ask a variant of bbarr's answer or something similar to m4no's answer, something like, "If I were to ask a member of the other tribe, 'Is this the correct road,' would he say 'yes?'"

Then do the opposite of what he says (the truth teller would tell the truth about the liar, or the liar would lie about the truth).

Is this what you were looking for?

Nemesio
Well actually isn't that more of a variation of your answer? The logic behind it is the same is what I mean.

The orignal answer to this is:

&quot;If I were to ask the other guy what he would say you would say is the correct road, what would his answer be?&quot; Then go down which ever road he says is the correct one.

But I like the simpler version you gave, mine was just a trap for all those who'd give the answer to the &quot;classic&quot; two guards puzzle. ðŸ˜€

[u]MÅ¥HÅRM[/u]