Normally about 1/2lb per person is what you end up with. Unless, of course, it's really good.
45 people
158,478
Twenty.
Ten
About a hundred people.
25
About 12 people if it is part of a 3 veg meal.
20-25 lbs
Just throw as much as you want in.
a lot
45
Depends on the size. If its about 25 lbs you need 2 turkeys.