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SingaporeMathsQuick questions

Probability and Statistics

Quick questions on Probability rules explained: H2 Mathematics Probability and Statistics

5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is the complement rule?
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The complement A′A' is "AA does not happen":
What is not reducing counts without replacement?
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After each draw without replacement, both the favourable and total counts decrease.
What is q1?
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If P(A)=0.3\mathrm{P}(A) = 0.3, find P(A′)\mathrm{P}(A'). [1 mark]
What is q2?
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Events AA and BB are mutually exclusive with P(A)=0.2\mathrm{P}(A) = 0.2, P(B)=0.5\mathrm{P}(B) = 0.5. Find P(A∪B)\mathrm{P}(A \cup B). [2 marks]
What is q3?
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Explain why "at least one" problems are often solved by the complement. [2 marks]

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