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2.3 Probability

2.3 Probability

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Question 163

A jar contains a large number of marbles. There are two colors of marbles in the jar:

  • 30% are Red (R)
  • 70% are Blue (B)

A student picks a marble at random, records its color, and replaces it in the jar. They then pick a second marble at random.

a.

Calculate the probability that both marbles picked are the same color.

[2]
b.

Find the probability that both marbles are Red, given that at least one of the marbles is Red.

[4]
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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