[jba]

we need at least three cards 9-K, right?

assuming no known hole cards

the number of boards containing at least three cards 9-K is:

(20*19*18*49*48/5!)

and the total number of boards:

C(52,5)


probability of the board precluding a low is (20*19*18*49*48/5!) / (52*51*50*49*48/5!)

0.0515837104

or about 1/20 hands.