[Ricks]

You are correct if we make the assumption that nobody would fold with a King in their hand. We could then say with certainty that there are only 39 unseen cards. My assumption that any of the five opponents will play any King actually has nothing to do with my calculation, now that I look at it.

1 - c(37,10)/c(39,10) = 1 - 348330136/635745396 =~ 0.452


I think that making the assumption that nobody would fold with a King is incorrect since there are many unplayable hands that include a King, even at 3/6. I understand your point though. It is certainly more likely that the hands that folded did not contain a King than hands that did contain a King. I have seen these points debated in the Probability forum and I'll see if i can dig some up.