Year 11
Higher

Year 11
Higher

# Calculate probabilities of independent events

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## Slide deck

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## Lesson details

### Key learning points

1. In this lesson, we will learn how to calculate probabilities of outcomes for independent events from tree diagrams

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This content is made available by Oak National Academy Limited and its partners and licensed under Oak’s terms & conditions (Collection 1), except where otherwise stated.

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## Starter quiz

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### 3 Questions

Q1.
Here is the first branch of a probability tree diagram.
Correct answer: A
B
C
D
Q2.
Here is the first branch of a different probability tree diagram. What should the missing probability be?
Correct answer: 0.18
0.41
0.82
18
Q3.
This tree diagram shows Amir taking red and blue counters from a jar. He replaces the counter after he has picked one up.
A
B
Correct answer: C
D

## Exit quiz

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### 3 Questions

Q1.
For the probability tree shown, which calculation will find the probability of red followed by blue happening?
0.2 + 0.2
0.2 x 0.2
Correct answer: 0.2 x 0.8
0.8 x 0.8
Q2.
The probability that Amy and Joe win a game of chess is shown in the tree diagram. Work out the probability that over 2 games Amy wins twice.
Correct answer: 0.09
0.49
0.6
0.9
Q3.
James draws this probability tree diagram to help him calculate probabilities of taking sweets from a bag. What assumptions has James made when completing this probability tree?
All probabilities add to 1 on each branch.
Correct answer: He replaces the first sweet he takes.
It doesn’t matter if he eats the first sweet he takes.