Probability · Combined events & tree diagrams
Chapter 1 · 3
The idea
Tree diagrams & independent events
Building a tree from a worded scenario, and why you multiply along a branch and add between branches — plus the branches-sum-to-1 check and the "at least one" complement that turns seven calculations into one.
A full journey — read it, play with it, work it, then earn real exam marks. Everything stays on the timeline below.
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Probability · Combined events & tree diagrams
Tree diagrams & independent events
Building a tree from a worded scenario, and why you multiply along a branch and add between branches — plus the branches-sum-to-1 check and the "at least one" complement that turns seven calculations into one.
Why it works
The picture of "this, then that"
A two-stage experiment is just this happens, then that happens. A tree diagram is the picture of exactly that: one set of branches for everything stage 1 could do, and then, growing out of the end of every one of those, a fresh set of branches for everything stage 2 could do. Follow a branch from the start to a tip and you have traced one complete outcome of the whole experiment. Everything after that is two rules, multiply along, add across — and both are consequences of what a probability is, not conventions to be memorised.Keep reading — free
The rest of the explanation, plus 3 worked examples you step through move by move.
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