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# AS-Level Maths | Probability
- URL: https://www.a-level-maths-tutor.com/as-level-maths-probability/
- Published: 2026-04-14T13:52:00.000Z
- Updated: 2026-04-23T13:00:03.000Z
- Author: Jaisul Naik
- Tags: Stats

###   
What does P(A) mean?

P(A) is the probability of A happening

### What does P(A') mean?

P(A') is the probability of A not happening

### What does P(A∩B) mean?

P(A∩B) is the probability of A and B happening

### What does P(AUB) mean?

P(AUB) is the probability of only A happening, or only B happening, or both A and B happening

### What does P(A|B) mean?

P(A|B) is the probability of A happening given that we know B is also happening.

### What does independent mean?

A and B are independent if **P(A∩B) = P(A) x P(B)**

### What does mutually exclusive mean?

A and B are mutually exclusive if **P(A∩B) = 0**

## Venn Diagrams

### Question 1

![](https://storage.ghost.io/c/37/0e/370e4698-c6d5-4470-8b24-7d14723fff86/content/images/2026/02/CleanShot-2026-02-13-at-13.40.36@2x.png)

### Question 2

![](https://storage.ghost.io/c/37/0e/370e4698-c6d5-4470-8b24-7d14723fff86/content/images/2026/02/CleanShot-2026-02-13-at-13.41.17@2x.png)

### Question 3

![](https://storage.ghost.io/c/37/0e/370e4698-c6d5-4470-8b24-7d14723fff86/content/images/2026/02/CleanShot-2026-02-13-at-13.41.45@2x.png)

## Probability Tree Diagrams

### Question 8

![](https://storage.ghost.io/c/37/0e/370e4698-c6d5-4470-8b24-7d14723fff86/content/images/2026/02/CleanShot-2026-02-13-at-13.53.53@2x.png)

### Question 9

![](https://storage.ghost.io/c/37/0e/370e4698-c6d5-4470-8b24-7d14723fff86/content/images/2026/02/CleanShot-2026-02-13-at-13.55.38@2x.png)

### Question 10

![](https://storage.ghost.io/c/37/0e/370e4698-c6d5-4470-8b24-7d14723fff86/content/images/2026/02/CleanShot-2026-02-13-at-13.56.19@2x.png)