JonC 101 / Brainteaser Collection / Difficulty 5/5 Questions
The basic setup for each problem is given below. For more details, hints, and a solution to each, click on the problem's title.
Title Difficulty Basic Setup

You are given 12 gold coins, however, you are later told that 1 of the 12 coins is a fake. The only way of discerning the fake coin from the real ones is by it's weight. All of the 11 real gold coins will weigh exactly the same amount each, while the fake coin will weigh EITHER more or less than each other coin.

The only tool you have available to you is a balance. This works simply by placing some coins on the left and right "pans" of the balance, and then activating the balance. Upon activation, the balance will simply state whether the left pan's contents are heavier, the right pan's contents are heavier, or they are equal in weight.

Click to learn what IS the fewest times you will need to use the balance to ferret out the fake coin What is the minimum number of times you will need to activate the balance (and how would you do it) to determine:

  1. Which coin is the fake and
  2. Is the fake coin heavier or lighter than the rest?

You are the eldest of 5 pirates, and fortune be with you, you discovered buried treasure of 100 gold pieces.

Being the oldest pirate, you get to decide how much each pirate's share will be. However, once you've laid out your plan, stating how much each pirate will get out of the 100, the 5 of you will take a vote as to whether they like the plan (your vote counts as well).

Once the vote is taken, if AT LEAST 50% of the vote is in your favor the pirates must abide by your decision of who gets what share. However, if you do NOT get at least 50% of the vote, the other pirates KILL you, and then the next oldest pirate gets to decide what shares the remaining pirates will get. Of course, even the next oldest pirate's plan would have to be voted on, making it possible that he could be voted out and killed and it would repeat for 3 pirates then 2, etc.

Assuming all 5 pirates, including you, are equally intelligent and all have only these goals: 1) Get as much gold as possible for themselves and 2) Stay alive,

What share would you specify for each pirate, and yourself, and how would you reason with the pirates to ensure you get enough of the vote to stay alive and keep your share?

brainteaser/difficulty5.htm | Page last updated $Date: 2003/11/30 09:12:50 $