The joy of the Poisson process is that it is ENTIRELY scalable.

"Ships pass a bird sanctuary at a Poisson rate of one per hour."

This is a Poisson process with , referring to ships per day.

"Twenty percent of the ships are oil tankers."

24*0.2 = 4.8

This is a Poisson process with , referring to oil tankers per day.

"1. What is the probability that at least one oil tanker will pass during 24 hours."

1 - P(0) = ??

"2. If 30 ships have past by in one day, what is the probability that 6 of them were oil tankers."

This is a very odd question. It seems to have little to do with whether or not we have a Poisson process. I'm thinking a binomial model would be more appropriate.

p(oil tanker) = 0.2 = p

p(not oil tanker) = 0.8 = q = 1-p

= ???

What is the complete term with in it?

I suppose, since 30 is a relatively large number, that some other approximation might be appropriate. The binomial is simple enough in this case that playing with other defininitions may be off the mark.