# Calculate Simple Probability

In this worksheet, students will work out the probability of an event happening.

Key stage:  KS 3

Curriculum topic:   Probability

Curriculum subtopic:   Record, Describe and Analyse Probability Experiments

Popular topics:   Probability worksheets

Difficulty level:

#### Worksheet Overview

Probabilities are written as fractions.

On the top of the fraction, we put the number of ways there are of your event happening.

On the bottom of the fraction, we put the total number of possible outcomes.

Reduce the fraction if you can by dividing both the top and bottom by the HCF

Example

There are 3 red balls and 5 blue balls in a bag.

What is the probability of choosing a red ball?

On the top of the fraction, we put the number of ways there are of your event happening.  This will be the number of red balls (i.e. 3)

On the bottom of the fraction, we put the total number of possible outcomes.  This will be the total number of balls (3 + 5 = 8)

The probability is 3/8

Does that make sense?

We're going to practise this now in a series of questions.

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