Before a knockout tournament with 2^n players I pick two players. What is the probability that they have to play against each other at some point in the tournament?

A weekly challenge concerning combinatorical probability.

Some relationships are transitive, such as `if A>B and B>C then it follows that A>C', but some are not. In a voting system, if A beats B and B beats C should we expect A to beat C?

Heads or Tails - the prize doubles until you win it. How much would you pay to play?

This article, for students and teachers, is mainly about probability, the mathematical way of looking at random chance.

It is believed that weaker snooker players have a better chance of winning matches over eleven frames (i.e. first to win 6 frames) than they do over fifteen frames. Is this true?

Calculate probabilities associated with the Derren Brown coin scam in which he flipped 10 heads in a row.

Two brothers belong to a club with 10 members. Four are selected for a match. Find the probability that both brothers are selected.

By tossing a coin one of three princes is chosen to be the next King of Randomia. Does each prince have an equal chance of taking the throne?

A player has probability 0.4 of winning a single game. What is his probability of winning a 'best of 15 games' tournament?

Can you devise a fair scoring system when dice land edge-up or corner-up?

In four years 2001 to 2004 Arsenal have been drawn against Chelsea in the FA cup and have beaten Chelsea every time. What was the probability of this? Lots of fractions in the calculations!

Uncertain about the likelihood of unexpected events? You are not alone!

How do scores on dice and factors of polynomials relate to each other?

Use combinatoric probabilities to work out the probability that you are genetically unique!