80 people were asked which social media apps they use: Instagram, TikTok, and Snapchat. 20 people use all three apps. 50 people use Instagram. 10 people use Instagram and TikTok but not Snapchat. 35 people use TikTok and Snapchat. 2 people do not use any of these apps. All 45 people who use Snapchat use at least one other app.
Two of the 80 people are chosen at random. Work out the probability that they both use TikTok.
28 exam-style questions on AQA GCSE Maths Conditional Probability. Each one has a worked solution and a mark scheme showing where the marks go.