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4MA1/1H Jun 2020, Question 15: Tree Diagrams for Independent Events

Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 1H (Higher) · Calculator · 5 marks

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The question, in short

Two fair five-sided spinners, A with 2 red and 3 green sections, B with 4 red and 1 green, are each spun once; find probabilities from a tree and for at least one green.

Summarised in our own words. Use the official paper for the exact wording and the diagram.

Part (a) · 2 marks

Fill in the missing probabilities on the tree for spinner A then spinner B outcomes.

  1. 1Spinner A has 2 red and 3 green, so P(red) = 2/5, P(green) = 3/5
  2. 2Spinner B has 4 red and 1 green, so P(red) = 4/5, P(green) = 1/5

Answer2/5, 3/5 and 4/5, 1/5

Part (b) · 3 marks

Calculate the chance that one or both spinners stop on green.

  1. 1P(both red) = (2/5) × (4/5) = 8/25
  2. 2P(at least one green) = 1 − P(both red)
  3. 31 − 8/25 = 17/25

Answer17/25

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