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0580/42 May/Jun 2025, Question 16: Tree Diagrams for Dependent Events

Cambridge IGCSE Mathematics 0580 · Paper 42 (Extended) · Calculator · 4 marks

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The question, in short

Given daily sunny probability 0.7, find the chance of not sunny, then use walk probabilities 0.9 when sunny and 0.2 when not to find the overall chance Rohit walks.

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Part (a) · 1 mark

Find the probability that the weather is not sunny on a day, given sunny probability 0.7.

  1. 1P(not sunny) = 1 − 0.7 = 0.3

Answer0.3

Part (b) · 3 marks

Using walk probability 0.9 when sunny and 0.2 when not sunny, find the probability Rohit goes for a walk on a day.

  1. 1P(sunny and walk) = 0.7 × 0.9 = 0.63
  2. 2P(not sunny and walk) = 0.3 × 0.2 = 0.06
  3. 3P(walk) = 0.63 + 0.06 = 0.69

Answer0.69

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Also searched as: 0580/42/M/J/25 · 0580_s25_qp_42 · 0580 s25 42 · question 16.
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