October 2009
9 posts
3 tags
Answer: Tuesday Teaser #6
Perhaps surprisingly, the best strategy will allow you to save 99 prisoners. To do this, we use a trick involving parity, which goes like so:
The prisoner at the back of the line can see 99 hats in front of him. Those hats are either white or black, so we have two possible scenarios - either there are an odd number of white hats and an even number of black, or there are an odd number of black...
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4 tags
Tuesday Teaser #6
A military general has 100 prisoners. Feeling generous, he offers them an opportunity to win their freedom. The next day, he’ll line up the prisoners, all facing forward, and will put either a black or a white hat on each prisoner. The prisoners can only see the colors of the hats in front of them. Then, in any order they want, each one will guess the color of the hat on their head. If they...
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Answer: Tuesday Teaser #5
I like the idea that you’d have two laptops purely for the purposes of breaking!
There are two key parts to this puzzle’s answer. Firstly, imagine you only have a single laptop. In this scenario there is only one way of finding out the maximum height, namely to start from the bottom and work up floor-by-floor until the laptop breaks.
Secondly, because we have two laptops, we can...
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Tuesday Teaser #5
I’m in a building with 20 floors and I have two laptops. I want to know the highest floor from which I can drop a laptop without it breaking. For the purposes of the puzzle, the laptop either breaks or works after each drop. Obviously after a laptop breaks, it can no longer be used, so I’m down to one. What is the least number of drops needed to identify the maximum height?