We have the variable "waiting time" as a random variable uniformly distributed between 0 and 7 minutes.
We have to find the probability that the waiting time is greater than 3.25 minutes.
We can see the probability as the "green" area in the
We can calculate this probabilty as:
NOTE: we can also have calculated the area (1/7)*(7-3.25) with the same result.
Answer: the probability of a waiting time greater than 3.25 is P(t>3.25)=0.536 or 53.6%.