This task/problem has been evolved as a result of Bush's administration ideas after '01 terror defence politics. Maybe it's not true, but homework is still valid:) So...
After WTC attacks USA administration established new program, which goal was to detect suspected people, which could be accused of being involved in terrorism. There were simple assumption, that if two (maybe unknown to each other) person have met in two different times on neutral area (i.e. hotel) they could be terrorists.
Assuming that:
- From 100 days everybody spends 1 in hotel (chance of being in hotel is 0,01%)
- There are 10 000 hotels in our research environment
- Every hotel have accomodation for 100 people
- Population of people being watched is 1 000 000 000
- Our research lasts 1 000 days
How many people (and why!) would be suspected after this program?
In addition, two meetings between two people could be taken in two different hotels.