# Conditional probability

**26**NRICH Mathematical resources connected to

**Conditional probability**

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### Do you brush your teeth every day?

How can we find out answers to questions like this if people often lie?

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### Drug testing

How do different drug-testing regimes affect the risks and payoffs for an athlete who chooses to take drugs?

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### Non-Transitive Dice

Alison and Charlie are playing a game. Charlie wants to go first so Alison lets him. Was that such a good idea?

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### At least one...

Imagine flipping a coin a number of times. Can you work out the probability you will get a head on at least one of the flips?

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### Mathsland National Lottery

Can you work out the probability of winning the Mathsland National Lottery?

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### Same Number!

If everyone in your class picked a number from 1 to 225, do you think any two people would pick the same number?

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### X-Dice

Explore these X-dice with numbers other than 1 to 6 on their faces.
Which one is best?