Cannibals and Villagers - Logic Problem

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Old 08-27-2021, 07:24 PM
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Default Cannibals and Villagers - Logic Problem

Three cannibals and three Villagers have to cross a river. The boat they have is only big enough for two people. If at any point in time there are more cannibals on one side of the river than Villagers, the cannibals will eat them. The boat can’t cross the river by itself, someone has to be in it to row it across.
What plan can the Villagers use for crossing the river so they don’t get eaten?

Note that if a boat with a cannibal and a Villager travels to a shore with one cannibal on it, then number of cannibals is greater than number of Villagers, even if you say the Villager immediately takes the boat back.

Answer coming soon.

Question 2 - Who are the three Villagers!!!! LOL

Last edited by JohnN; 08-29-2021 at 07:16 AM.
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Old 08-27-2021, 08:36 PM
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I watch too much of the Walking Dead. But then again these are not zombies but cannibals.

I have seen this puzzle before but it used other people.

Last edited by Taltarzac725; 08-27-2021 at 09:34 PM.
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Old 08-28-2021, 07:56 AM
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Quote:
Originally Posted by Taltarzac725 View Post
I have seen this puzzle before but it used other people.
Answer
So initially there are Three Cannibals and Three Villagers all are on west coast of river. They are supposed to cross over river to reach east coast by boat.

Step 1:
1 Cannibal and 1 Villager cross over river and then Villager comes back to west coast.
So now there are 2 Cannibals and 3 Villagers left to cross river while 1 Cannibal is on other side of river.
Step 2:

2 Cannibals cross over river and then 1 Cannibal comes back to west coast.

So now there are 1 Cannibals and 3 Villagers left to cross river while 2 Cannibals are on other side of river.
Step 3:

2 Villagers cross over river and then 1 Cannibal and 1 Villager come back to west coast.
So now there are 2 Cannibals and 2 Villagers left to cross river while 1 Cannibal and 1 Villager are on other side of river.
Step 4:

2 Villagers cross over river and then 1 Cannibal come back to west coast.
So now there are 3 Cannibals left to cross river while 3 Archaeologists are on other side of river.
Step 5:

2 Cannibals cross over river and then 1 Cannibal comes back to west coast.

So now there are 2 Cannibals left to cross river while 1 Cannibal and 3 Villagers are on other side of river.
Step 6:

Remaining 2 Cannibals cross over river. So now all 3 Cannibals and 3 Villagers have crossed the river.
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Old 08-28-2021, 08:01 AM
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An old, but thought provoking problem. The original was the cannibal/missionary scenario and there is a closely related 'jealous husbands' problem. Thanks for posting.
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Old 08-28-2021, 08:22 AM
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The answer to this could be a lot easier given the assumption that at least one and three Villagers is packing a firearm.
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Old 08-28-2021, 09:07 AM
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Originally Posted by tophcfa View Post
The answer to this could be a lot easier given the assumption that at least one and three Villagers is packing a firearm.
That's why I was thinking of zombies and The Walking Dead.

Propositiones ad Acuendos Juvenes - Wikipedia

This dates to probably around the 780s or even earlier. Alcuin (735 - 804) - Biography - MacTutor History of Mathematics

Last edited by Taltarzac725; 08-28-2021 at 09:14 AM.
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Old 08-28-2021, 09:29 AM
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The three cannibals ARE the three Villagers. They have no trouble co-existing with each other. They're in the same tribe.
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Old 08-28-2021, 09:37 AM
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That is all well and good, except one of the cannibals has a clip board and is reporting EVERYTHING that the Villagers are doing wrong. Eventually the Villagers get sick and tired of their constant reporting and throws them all into the river !!!!!! And all is now happy and the boat is fully adorned with ornaments !
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Old 08-29-2021, 05:01 AM
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Quote:
Originally Posted by SIRE1 View Post
That is all well and good, except one of the cannibals has a clip board and is reporting EVERYTHING that the Villagers are doing wrong. Eventually the Villagers get sick and tired of their constant reporting and throws them all into the river !!!!!! And all is now happy and the boat is fully adorned with ornaments !
Unless one of them stepped in dog poop and got it in the boat... Phewww...
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Old 08-29-2021, 05:55 AM
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Quote:
Originally Posted by JohnN View Post
Three cannibals and three Villagers have to cross a river. The boat they have is only big enough for two people. If at any point in time there are more cannibals on one side of the river than Villagers, the cannibals will eat them. The boat can’t cross the river by itself, someone has to be in it to row it across.
What plan can the Villagers use for crossing the river so they don’t get eaten?

Note that if a boat with a cannibal and a Villager travels to a shore with one cannibal on it, then number of cannibals is greater than number of Villagers, even if you say the archaeologist immediately takes the boat back.

Answer coming soon.

Question 2 - Who are the three Villagers!!!! LOL
Why not just use the bridge?
  #11  
Old 08-29-2021, 06:13 AM
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Where did the archaeologist come from?
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Old 08-29-2021, 06:35 AM
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[QUOTE=JohnN;1995570]Answer
So initially there are Three Cannibals and Three Villagers all are on west coast of river. They are supposed to cross over river to reach east coast by boat.

Step 1:
1 Cannibal and 1 Villager cross over river and then Villager comes back to west coast.
So now there are 2 Cannibals and 3 Villagers left to cross river while 1 Cannibal is on other side of river.
Step 2:



2 Cannibals cross over river and then 1 Cannibal comes back to west coast.

So now there are 1 Cannibals and 3 Villagers left to cross river while 2 Cannibals are on other side of river.
Step 3:

2 Villagers cross over river and then 1 Cannibal and 1 Villager come back to west coast.
So now there are 2 Cannibals and 2 Villagers left to cross river while 1 Cannibal and 1 Villager are on other side of river.
Step 4:

2 Villagers cross over river and then 1 Cannibal come back to west coast.
So now there are 3 Cannibals left to cross river while 3 Archaeologists are on other side of river.
Step 5:

2 Cannibals cross over river and then 1 Cannibal comes back to west coast.

So now there are 2 Cannibals left to cross river while 1 Cannibal and 3 Villagers are on other side of river.
Step 6:

Remaining 2 Cannibals cross over river. So now all 3 Cannibals and 3 Villagers

If the cannibals and the villagers are all on one side at first there wouldn’t be any Villagers uneaten to make the journey across the river in the first place.
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Old 08-29-2021, 07:00 AM
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Default Canibals

Why don’t cannibals eat clowns?


They taste funny
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Old 08-29-2021, 07:17 AM
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Quote:
Originally Posted by Mrprez View Post
Where did the archaeologist come from?
LOL - good catch, I corrected it to Villager. My son is an archaeologist and I'd sent it to him modified that way.
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Old 08-29-2021, 08:10 AM
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Quote:
Originally Posted by JohnN View Post
Three cannibals and three Villagers have to cross a river. The boat they have is only big enough for two people. If at any point in time there are more cannibals on one side of the river than Villagers, the cannibals will eat them. The boat can’t cross the river by itself, someone has to be in it to row it across.
What plan can the Villagers use for crossing the river so they don’t get eaten?

Note that if a boat with a cannibal and a Villager travels to a shore with one cannibal on it, then number of cannibals is greater than number of Villagers, even if you say the Villager immediately takes the boat back.

Answer coming soon.

Question 2 - Who are the three Villagers!!!! LOL
This is a trick question.

No self-respecting cannibal would EVER eat a Villager. Too tough.
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