So I know there are some pretty smart people on here (and even more dumbasses). Anyways my math teacher recently assigned an extra credit problem I was looking to get some help from people on here. If you do understand how to do this problem, I am not just looking for an easy answer, I would like to understand the steps used to get to that answer.
Anyways here is the question.
There are four large groups of people, each with 1000 members. Any two of these groups have 100 members in common. Any three of these groups have 10 members in common. Ad there is one person in all four groups. all together how many people are in these four groups