If arrivals occur at a mean rate of 3.6 events per hour, the exponential probability of waiting more than 0.5 hour for the next arrival is:

The answer is 0.8347. Mean u = 1/m = 3.6 per hour Time x = 0.5 hour Exponential Probability = P (X < = x) Going by the Cumulative distribution function P (X < = x) = 1 - e^ (-mx) P (X <.5) = 1 â€" exp^ (-3.6 x 0.5) = 1 â€" 0.1653 = 0.8347