Chrome,

Straight or Flush draw is as follows : (where c=club d=diamond h=heart s=spade).

I Hold 8c,9c
and the flop is 7h, 6c, Kc,
and the turn is Qd

My best drawing hands at this stage are the open ended straight ( 6,7,8,9 ) or a flush ( need 1 more club)

Based on the cards we have seen (well those in our hand and the table) we have 16 outs. (4s,4d,4h ,Th,Td,Ts give a straight) and the clubs ( Ac, Qc, Jc, 7c, 5c,4c,3c,2c, for the straight) and 4c or Tc, (giving a straight and flush).

Count these up and you have 16 cards. So 15 outs was wrong. There are actually 16 outs or 16 cards that could appear on the river to provide a winning hand.

Since the deck is 52 cards and we already know 6 of those cards, we can calulate we have a 16/46 (or 34%) of hitting a winner.

Now it all comes down to pot odds in a ring game on whether to play the hand. As this was a tournament game I would go either way depending on what I felt the other player had.

Oh course if we looked at this just after the flop it would be a different story. Chances of hitting 1 card needed on the turn or river to get a flush is 1.75 to 1 against hitting it (which are not bad odds) It is similar with the straight hitting an open ended straight is approx 2.3 to 1 against hitting it on the turn or river.

Anyway hope that helps explain it ... I am not sure where 50% came from with Mr J.

Good Luck.