Monday, November 07, 2011

Greedy Logical Pirates

Here's a little logic puzzle from a book my old roommate Blake gave me many years ago. I really liked this one when I read it (I believe I've told it to a few people over the years) and I've been doing some other reading recently that reminded me of it. Can you figure it out?

There are five pirates who discover some buried treasure on an island. There are 100 gold coins and they need to divide the coins up amongst themselves. The way their pirate code works is the lead pirate proposes a split of the coins and then all the pirates vote on that proposal. If at least half the pirates vote YEA then that split carries and they move on with their plundering lives with their new booty. Otherwise they execute the lead pirate and start over from the top with the next pirate in line making a proposal.

The pirates are all greedy, logical, and don't want to die. You're the lead pirate. What split do you propose? Why?

1 comment:

Sky said...


You get 98 bucks every time.

I rank the pirates from 1-5 where 1 is the highest rank. Noted as r1, r2, r3, r4, r5.

In a two pirates scenario r4 proposes 100/0 and wins, so r5 must not let that happen. Therefore r5 will take even 1 coin in the 3 pirate situation.

In the 3 pirate situation r3 can then offer 99/0/1 and get it, therefore r4 will take any amount in the 4 pirate situation.

In the 4 pirate situation r2 can offer 99/0/1/0 and win, therefore r3 and r5 must not allow the 4 pirate situation to occur.

In the 5 pirate situation r1 can offer 98/0/1/0/1 and r3 and r5 still have to vote for it.

In the 3 pirate situation rank 3