Question

Christine Wong has asked Dave and Mike to help her move into a new apartment on Sunday morning. She has asked them both, in case one of them does not show up. From past experience, Christine knows that there is a 55% chance that Dave will not show up and a 45% chance that Mike will not show up. Dave and Mike do not know each other and their decisions can be assumed to be independent. a. What is the probability that both Dave and Mike will show up

Answer 1

a) 26.79%, b) 50.42% and c) 22.79%

Explanation:

a. What is the probability that both Dave and Mike will show up?

As decisions of showing up can be assumed to be independent, the probability will be given by

(1-0.53)(1-0.43)=(0.47)(0.57)=0.2679=26.79%

b. What is the probability that at least one of them will show up?

There are two possibilities for this to happen:

Dave shows up but Mike does not. The probability of Dave to show up is (1-0.53)=0.47 and the probability that Mike does not is 0.43. Then, as these events are independent, the probability for both of them to happen is (0.47)(0.43)=0.2021=20.21%

Mike shows up but Dave does not. The probability of Mike to show up is (1-0.43)=0.57 and the probability that Mike does not is 0.53. Then, as these events are independent, the probability for both of them to happen is (0.57)(0.53)=0.3021=30.21%

Therefore, the probability that at least one of them will show up? is 20.21%+30.21%=50.42%.

c. What is the probability that neither Dave nor Mike will show up?

As decisions of showing up can be assumed to be independent, the probability will be given by

(0.53)(0.43)=0.2279=22.79%