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Complementary events

CONCEPTUAL
MathematicsProbability|Ages 11—13|ID: mt_XfyqXLqzpx

Understand and apply the rule that probabilities of all mutually exclusive outcomes sum to one; use this to find the probability of a complementary event (P(not A) = 1 − P(A))

Mastery Evidence

  • Verify that probabilities of all outcomes listed for a spinner sum to 1
  • Calculate the probability of NOT rolling a 6 as 1 − 1/6 = 5/6
  • Identify an error in a probability distribution where the values do not sum to 1

Assessment Prompt

“If a spinner has three sections and one has a probability of 0.4 and another has 0.35, can [child] work out the probability of landing on the third section without being told?”

Curriculum Standards3 alignments

7.SP.5Common Core State Standards for Mathematics
Understand that the probability of a chance event is a number between 0 and 1

Understand that the probability of a chance event is a number between 0 and 1 that expresses the likelihood of the event occurring. Larger numbers indicate greater likelihood. A probability near 0 indicates an unlikely event, a probability around 1/2 indicates an event that is neither unlikely nor likely, and a probability near 1 indicates a likely event.

SP
7.SP.7aCommon Core State Standards for Mathematics
Develop a uniform probability model

Develop a uniform probability model by assigning equal probability to all outcomes, and use the model to determine probabilities of events. For example, if a student is selected at random from a class, find the probability that Jane will be selected and the probability that a girl will be selected.

SP
KS3.Maths.Prob.2The national curriculum in England
Sum of Probabilities

understand that the probabilities of all possible outcomes sum to 1

Mathematics · Key Stage 3

Prerequisites2

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