A tech support center receives inquiries through three channels: Phone, Email, and Live Chat. 45% of inquiries come through Phone, 40% through Email, and 15% through Live Chat.
The probability that an inquiry remains unresolved after the first contact is:
Draw a tree diagram to illustrate this situation.
An inquiry is selected at random. Find the probability it is unresolved.
Given that an inquiry is unresolved, find the probability it was made via the Phone channel.
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.