Working backwards to find a missing tree probability Revision Card | Tope Teaches Maths

AI generatedProbabilityKS3 / GCSE

Working backwards to find missing tree probability.

At each split, the outgoing probabilities sum to 1.
Multiply along a route; add mutually exclusive routes that meet the question.
Without replacement, update the counts and total for the second draw.

Example 1

The tree shows = and = . Find .

Multiply along the A then B route.

Divide the joint probability by

.

Example 2

The tree shows = and = . Find .

Multiply along the A then B route.

Divide the joint probability by

.

Your turn

Question 1

The tree shows = and = . Find .

Check answer

Multiply along the A then B route.

Divide the joint probability by

.

Question 2

The tree shows = and = . Find .

Check answer

Multiply along the A then B route.

Divide the joint probability by

.

Question 3

The tree shows = and = . Find .

Check answer

Multiply along the A then B route.

Divide the joint probability by

.

Question 4

The tree shows = and = . Find .

Check answer

Multiply along the A then B route.

Divide the joint probability by

.

Question 5

The tree shows = and = . Find .

Check answer

Multiply along the A then B route.

Divide the joint probability by

.

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