MATH-2820 Lecture 2: Probability

3. Chris knows that his chance to catch an elevator without having to wait for it on a Monday is 1, while on a Tuesday or a Wednesday, he is twice as likely to wait as he is not to wait. He will choose one of these days: Monday with probability 0.4, Tuesday with probability 0.3, and Wednesday with probability 0.3 for his elevator ride. What is the probability that he has to wait for the elevator? (A) 0.8 (B) # (C (D) E) 0.6

24. Umbuggio has two microphones which he uses to teach in RH100; one is Sony and one is Telefunken. The Sony fails with probability .3, while the Tele- funken fails with probability 4. On Monday morn- ing, Umbuggio picks a microphone at random. What is the probability that it will fail? (a) .7 (b) .35 (c) .12 (d) .58 (e) .42 (f) none of the above