Thursday, August 26th, 2010
I've wanted for a while to write simple python simulations of the birthday puzzles I'd written about previously. Then, recently, I was wondering what the most efficient way to tell if a list has duplicate elements. It suddenly dawned on me that these two topics were related:
The ...
Posted in programming | No Comments »
Friday, April 30th, 2010
Here's two classic birthday puzzles:
How many people do you need in a room to have a better than 50% chance of finding at least one shared birthday among them?
[ddet Answer]
Like a lot of these problems, it's easier to first find the chances of the proposition not happening - ...
Posted in puzzles | 2 Comments »
Thursday, April 29th, 2010
You deal the first 13 cards from a well shuffled, 52-card deck to someone. What are the chances the 13 cards you deal are of the same suit?
[ddet Answer]
There's a couple of ways to do this - both incorporate useful techniques for solving these kind of problems.
The first way ...
Posted in puzzles | 1 Comment »
Sunday, April 25th, 2010
Let's say you're playing a coin-tossing game. You start with $10 and are looking to double your money. The game is very simple: you pick an amount to wager on each toss, and if you toss heads you win the amount you wagered (as well as keeping ...
Posted in puzzles | 1 Comment »
Friday, April 23rd, 2010
Let's say that you're playing a coin-tossing game, and you start with $1. You keep tossing forever, winning $1 if you toss heads, and losing $1 if you toss tails. What are the chances you'll eventually go bust (get to $0)? What are the chances you'll ...
Posted in mathematics, puzzles | 1 Comment »
Saturday, April 10th, 2010
I want to revisit a probability puzzle from a previous post: see problem #5 in http://rebrained.com/?p=20
You play a game where you alternate tossing a coin with a friend, and the first person to toss heads wins. But let's make it a little more interesting by making the coin ...
Posted in puzzles | No Comments »
Wednesday, April 7th, 2010
Let's say there are 100 people, including you, waiting to board a fully booked flight, each with an assigned seat. The first person to board doesn't pay any attention to his assigned seat, and sits somewhere at random. Each of the subsequent people will sit in their ...
Posted in puzzles | 2 Comments »
Thursday, December 31st, 2009
This is another probability question that seems straightforward but can be deceptive...
You're an FBI agent and have been monitoring a large gang, and you know that 1/4 of its members always tell the truth, the rest always lie. Then you get taken hostage by the gang, and two gang members ...
Posted in puzzles | No Comments »
Sunday, June 1st, 2008
Some probability questions/puzzles:
1. I have two children. One of my children is a girl. What are the chances I have two girls?
[expand title=Answer]
The answer to the question as stated is not 50/50. After being told that one of your children is a girl, you know there are 3 options (with ...
Posted in puzzles | 7 Comments »