Probability tree diagrams
Learn Probability tree diagrams for Years 9–11 pupils (ages 13–16). Free practice questions, lessons and worked examples — aligned to the UK National Curriculum.
What you'll learn
- 1
A tree diagram shows every outcome of two or more events, with a probability written on each branch.
- 2
Multiply ALONG the branches to get the probability of a combined outcome. Add BETWEEN branches for "or".
- 3
To find the probability of two events both happening, what do you do?
- 4
If an item is NOT replaced, the second set of probabilities changes — the total has gone down by one.
- 5
A bag has 3 red and 2 blue. P(red then red) with no replacement = 3/5 × 2/4 = 6/20 = 3/10.
- 6
P(A) = 0.6 and P(B) = 0.5, independent. What is P(A and B)?
- 7
What must the branches from a single point add up to?
Practise Probability tree diagrams with Whizlo
Free AI-tutored lessons, unlimited practice questions, and progress tracking for ages 13–16. Aligned to the UK National Curriculum.