AC9M8P01Year 8ProbabilityPractised on site

AC9M8P01 — Year 8 Probability

Official Curriculum Content Description:

recognise that complementary events have a combined probability of one; use this relationship to calculate probabilities in applied contexts

Worked Examples (1)

Example 1Complement Rule (P(not A) = 1 - P(A))

The probability of event

A

occurring is

P(A) = \frac{7}{10}

. Find the probability of its complement,

P(A')

, which is the probability of event

A

not occurring. Express your answer as a fraction in its lowest terms.

Common mistake: Returning the probability of the event itself (

P(A) = \frac{7}{10}

) instead of subtracting it from

1

Correct Answer:

3/10

Worked Solution:

Using the complement rule

P(A') = 1 - P(A)

1 - \frac{7}{10} = \frac{10 - 7}{10} = \frac{3}{10}

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