Nine people are seated at three tables.
There are three people per table.
Each person meets with each of the others exactly twice.
How many days do they need to meet?

Answer:
8 days
Day 1 and 2 = ABC, DEF, GHI
Day 3 and 4 = ADE, BFI, CGH
Day 5 and 6 = AFG, BDH, CEI
Day 7 and 8 = AHI, BEG, CDF