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2.3 Probability

2.3 Probability

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Question 47

A researcher surveys 100 teenagers about their social media usage. The apps tracked are Snapchat (SSS), Instagram (III), and TikTok (TTT).

  • 10 teenagers use all three apps
  • 20 teenagers use both Snapchat and Instagram
  • 18 teenagers use both Instagram and TikTok
  • 25 teenagers use both Snapchat and TikTok
  • 50 teenagers use Snapchat
  • 45 teenagers use Instagram
  • 55 teenagers use TikTok
a.

Draw a Venn diagram to represent this information.

[3]
b.

One of the teenagers is selected at random. Given they use TikTok, find the probability they do not use Instagram.

[3]
Markscheme

2.3 Probability Questions

  1. A Level
  2. /Maths
  3. /2.3 Probability

200 exam-style questions on OCR (MEI) A Level Maths 2.3 Probability, covering 2.3.1 Calculate the probability of an event, 2.3.2 Complementary events, 2.3.3 Expected frequency of an event, 2.3.4 Diagrams to calculate probabilities, 2.3.5 Mutually exclusive and independent events, 2.3.6 Add probabilities for mutually exclusive events, 2.3.7 Multiply probabilities for independent events, 2.3.8 Mutually exclusive and independent events (notation) (A-level only), 2.3.9 Venn diagrams for probabilities (A-level only), 2.3.10 Conditional probabilities (A-level only), and 2.3.11 Independence via conditional probability (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.

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