4MA1/2H Jun 2023, Question 20: Tree Diagrams for Dependent Events
Pearson Edexcel International GCSE Mathematics A 4MA1 · Paper 2H (Higher) · Calculator · 3 marks
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The question, in short
Find the probability that at least one of 3 red counters among 12 (9 green) remains after three people each draw one at random.
Summarised in our own words. Use the official paper for the exact wording and any diagrams.
Solution · 3 marks
- 1A red stays in the bag unless all 3 reds are taken.
- 2P(all 3 taken are red) = 3/12 × 2/11 × 1/10 = 1/220
- 3P(at least one red left) = 1 − 1/220 = 219/220
Answer219/220
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