If I have 1000 identical objects that I need to distribute over 5 bins with the restraint that there can't be less than 40 in each bin, in how many ways can the distribution be done in?
I think that I first need to take $$\frac{\binom{1000}{120}}{5}$$
Now we have distributed 40 objects into each container. The rest comes from doing a partition, with the remaining objects.
$$\displaystyle\binom{n+k-1}{k-1} = $$ $$\displaystyle= \frac{(n+k-1)!}{(k-1)!(n-k)!}$$
And finally I combine the two calculations by multiplying them?