The time X to wait in line is an exponential distributed random variable with mean 5 minutes. Find the probability that the total waiting time will be longer than 30 minutes from the time that individual arrived in line, given that the wait has already been 20 minutes.

step-by-step explanation:

where is the question is there is a formula or is there not one

in counting the number of heads in 4 coin flips, the probability that we get exactly one head is the probability that we get anyone of the following 4 outcomes: httt, thtt, ttht, or ttth. each has probability 1/16, so the probability to get exactly one head in 4 flips is 1/16 + 1/16 + 1/16 + 1/16 = 4/16 = 1/4.

multiply each number by ten to get a simplified answer of 7/1.