9709 P63 - Jun 2019 - Q2
2597
Megan sends messages to her friends in one of 3 different ways: text, email or social media. For each message, the probability that she uses text is 0.3 and the probability that she uses email is 0.2. She receives an immediate reply from a text message with probability 0.4, from an email with probability 0.15 and from social media with probability 0.6.
(i) Draw a fully labelled tree diagram to represent this information.
(ii) Given that Megan does not receive an immediate reply to a message, find the probability that the message was an email.
