If you assume 3, average utilitarianism says you should kill anyone who has below average utility, since that raises the average. So in the end you kill everyone except the one person who has the highest utility.
You really need to also assume killing people doesn’t decrease utility for those who are left, which usually doesn’t work too well for humans...
You really need to also assume killing people doesn’t decrease utility for those who are left, which usually doesn’t work too well for humans...