# of tables needed in a restaurant...

Hi,

Here is the problem statement:

On an average 5 families visit a restaurant every hour and each family takes exactly an hour to finish eating. How many tables should the restaurant management make available, if the prob of a family waiting for a table is not to exceed 0.2. (Other info: total N families in city and the probability of each family visiting the restaurant at any given time is 'p')

There is no mention of an exponential rate of arrival, so not sure how to tackle this problem.

Mean = 5 = Np

Let the no of tables be C. One approach would be to calculate the probability of more than C families arriving at the restaurant in one hour:

Not sure where I am going with it and how to figure out C... any help is appreciated.

Thanks