Stage: 4 Challenge Level: 
What is the chance that one person's birthday is different from that of another person chosen at random ?
So what is the chance that their birthdays do match ?
Given that the first two did not match, what is the chance that a third person will not match with either of those first two ?
Can you now calculate the probability that all three birthdays are different ?
So what is the chance that their birthdays do match ?
Given that the first two did not match, what is the chance that a third person will not match with either of those first two ?
Can you now calculate the probability that all three birthdays are different ?
Conditional probability. Combining probabilities. Real world. Theoretical probability. Tree diagrams. Equally likely outcomes. Random variables. Quadratic equations. Long problems. Experimental probability.
Published November 2005,December 2005.
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