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4024/13 May/Jun 2025, Question 10: Basic Probability

Cambridge O Level Mathematics 4024 · Paper 13 (Non-calculator) · Non-calculator · 3 marks

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The question, in short

A spinner has four colours with probabilities given in a table; one value is wrong. Explain why, then find the correct probability for blue.

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

Part (a) · 1 mark

State why the four probabilities in the table cannot all be correct.

  1. 10.35 + 0.2 + 0.15 + 0.4 = 1.1
  2. 2The probabilities add up to more than 1, but they must add up to exactly 1

AnswerThe probabilities add up to more than 1

Part (b) · 2 marks

Given the blue value is wrong, calculate the correct probability of landing on blue.

  1. 10.35 + 0.2 + 0.15 = 0.7
  2. 2P(blue) = 1 − 0.7 = 0.3

Answer0.3

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