Year 9 Probability
Tree Diagrams — Two-Stage Experiments
Complete the pre-drawn trees: write each possibility at the branch tips and each branch probability as a fraction, then read answers straight off the paths.
20 questions · one per page
Draw it, label it, put a fraction on every branch.
Spinners spun twice, counters drawn from bags, letters picked from words, cards taken from piles. The tree is already drawn for you — you complete it: each possibility at the end of the branches, and each branch's probability as a fraction above or below the line. The questions then grow from fair coins to draws without replacement, where the second stage is out of one fewer.
How every question works
Step 1: type the outcomes on the branch tips. Step 2: write the fraction on each branch. Then: multiply along a path for P(A and B), add the paths you want, and use 1 − P(none) for "at least one".
Method
Worked model
Unit complete
Tree diagrams, mastered.
The student has completed sample-space trees for fair and uneven experiments, with and without replacement, placed a probability fraction on every branch, and combined paths to find "at least one" and comparison answers.