This is as far as my poor geometry skills have got me. I'm having people sit around a table and want them spaced at least one metre apart when from different households. X represents the distance between two people from different households. The line a represents the distance between two people from the same household.
This isn't an exam question. I'm setting up wedding tables and need people spaced a metre apart.
The tables we have are 6 feet so r=3, and a I would guess to be 2.
The minimal diameter of the table to seat 3 pairs is calculated - It is 4.16 foot.
I assume that this answers your question.