What is it
KS3 probability builds on earlier work to cover calculating probabilities from sample spaces, using probability trees for combined events, and understanding mutually exclusive and independent events.
Why it matters
Probability trees are the tool that makes multi-step probability problems manageable — a visual structure that turns what looks like a complex calculation into a series of simple multiplications and additions.
Exam tip
On a probability tree, always check that the probabilities on each pair of branches add up to 1 before multiplying along any path — this simple check catches most set-up errors early.
Related topics
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