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2.3 Probability

2.3 Probability

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Question 151

In a botanical survey of a large woodland area, trees are classified as being either Deciduous or Evergreen.

Of the Deciduous trees, 90% are found to be carrying a specific fungal infection. Of the Evergreen trees, 25% are found to be carrying the same infection.

The proportion of trees in the woodland that are Deciduous is kkk.

a.

Draw a tree diagram to represent this information.

[2]
b.

In the survey, 70.5% of all trees were found to be carrying the infection.

Find the value of kkk.

[3]
c.

One tree is selected at random from the woodland. Given that this tree is infected, find the probability that it is a Deciduous tree.

[2]
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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