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Rain or Shine

Predict future weather using the probability that tomorrow is wet given today is wet and the probability that tomorrow is wet given that today is dry.

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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?

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If the score is 8-8 do I have more chance of winning if the winner is the first to reach 9 points or the first to reach 10 points?

How Many Balls?

Stage: 5 Challenge Level: Challenge Level:1
Decide on the unknowns and assign letters to them. Take the information given step by stepand write down expressions for the probabilities. Can you obtain an equation and solve it?