Question

A hotel has three clevators. One of themis a freight elevator. When pressing thebutton, one of the elevators randomlyservices your floor. If you use theclevators six times, what is the probabilitythat you use the freight elevator at leasttwo times?

Answer 1

You take into account that the probability of getting the freight elevator in one case. Such a probabilty is given by:

p = 1/3 because there are three elevator

For the case in which you use the elevator six times, the probability of getting the freight elevator will be:

P = 2/(3*6) = 2/18 = 1/9

where it is taken into account that the total number of moments in which the elevator is used.