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2.3 Probability

2.3 Probability

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Question 146

At a school, the event I I\,I is that a randomly chosen student plays a musical instrument, and the event C C\,C is that the student sings in the choir.

It is known that P(I)=320P(I)=\dfrac{3}{20}P(I)=203​, P(I∩C)=120P(I\cap C)=\dfrac{1}{20}P(I∩C)=201​ and P(I∣C)=514P(I\mid C)=\dfrac{5}{14}P(I∣C)=145​.

a.

Find the probability that the student sings in the choir.

[3]
b.

Given that the student does not play a musical instrument, find the probability that the student sings in the choir.

[3]
Markscheme

2.3 Probability Questions

  1. A Level
  2. /Maths
  3. /2.3 Probability

200 exam-style questions on OCR A Level Maths 2.3 Probability, covering 2.3.1 Mutually exclusive and independent events, 2.3.2 Diagrams to assist probability calculations, 2.3.3 Conditional probability (A-level only), 2.3.4 Conditional probability from first principles (A-level only), and 2.3.5 Modelling with probability. Each one has a worked solution and a mark scheme showing where the marks go.

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