5.1.2

Sum of Probabilities

Test yourself

Sum of Probabilities

If all the possible outcomes of an event are listed then the sum of the probabilities of those events will be 1.

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Probabilities add up to 1

  • For any event:
    • P(event happens) + P(event doesn’t happen) = 1.
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Rules

  • The probabilities of a set of outcomes add up to 1 if:
    • All possible outcomes are included
    • Only one outcome can happen at a time.

Jump to other topics

1Number

1.1Using Numbers

1.2Fractions, Decimals & Percentages

1.3Powers & Roots

1.4Accuracy

2Algebra

2.1Introduction to Algebra

2.2Manipulating Algebra

2.3Proofs & Functions

2.4Straight Line Graphs

2.5Common Graphs

2.6Transformations & Tangents

2.7Properties of Graphs

2.8Solving Equations

2.9Inequalities

2.10Sequences

3Ratio

4Geometry

4.1Introduction to Geometry

4.2Triangles & Quadrilaterals

4.3Transformations

4.4Circle Basics

4.5Circle Theorems

4.6Measurements & Units

4.7Calculating Area

4.8Triangle Formulae

4.93D Shapes

4.10Vectors

5Probability

6Statistics

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