80 office workers were surveyed about which productivity apps they use: Slack, Zoom, and Trello. Every worker used at least one of these applications. 10 of the workers use all three applications. 35 of the workers use Trello. 45 of the workers use Slack. 22 of the workers use Slack and Zoom. 8 of the workers use Slack and Trello but not Zoom. 5 of the workers use Zoom and Trello but not Slack.
Two of the 80 workers are chosen at random. Work out the probability that they both use Zoom.
72 exam-style questions on OCR GCSE Maths Conditional Probability. Each one has a worked solution and a mark scheme showing where the marks go.