If you have to split up a circular foodstuff between an odd number(n where n = 3,5,7...) of person, always cut them such that the parts are 2n. That way you can equally distribute it to each person.

They should've spread the butter before cutting!
That way it would've been fairer too.

What, you guys can't just eyeball thirds? I cut pizzas into tenths, which involves making an eyeball estimation of a fifth.