of times a 5 will come up.
Now 600 times is a large number of rolls so we may as well use the normal
approximation to the binaomial distribution, in this case it will have mean:
and standard deviation:
So you would expect the number of 5's to be , where
the value of is chossen by you depending on what confidence you want
that the actual number lies in the interval, often a value of is used.