Part: Part Four - Pot Odds & Hand Analysis

Not all outs are clean

Pre-flop
Blinds 100 / 200Pot 900 (4.5 BB)BTNQ9 20,000 (100 BB)YOUto actMP 20,000 (100 BB)Openerraises 600 (3 BB)SB 20,000 (100 BB)posts 100 (0.5 BB)BB 20,000 (100 BB)posts 200 (1 BB)D

It folds to you on the button with Q♥9♥ after a middle-position raise.

Opener makes it 600 (3 BB); you hold Q♥9♥ on the button. Best?

WhyA suited, connected broadway plays fine in position against one raiser - just plan to read the board carefully, because not every draw it flops will be as clean as the raw out-count suggests.
What happensYou call and the blinds fold, taking a flop where the texture will matter more than the count. Pot: 1,500 (7.5 BB).
Flop
Heads-upPot 1,500 (7.5 BB)J104BTNQ9 20,000 (100 BB)YOUopen-ender, but two outs are 'tainted'MP 20,000 (100 BB)Openerbets 900 (4.5 BB)D

Flop: J♠ T♠ 4♦ - you flop an open-ended straight draw (any K or 8). But the board is two-spade, so the K♠ and 8♠ complete a flush for anyone on a spade draw.

Eight 'outs', but two of them (K♠, 8♠) can hand someone a flush. Your effective outs?

WhyTwo of your eight straight cards are the K♠ and 8♠ - the very cards that also complete a spade flush, so against a flush draw they make your straight and lose it anyway. Strip those out and you're on about six clean outs, roughly 24% by the rule of four, and facing a bet plus a possible raise on this wet board, that's a losing price.
What happensYou fold - overpaying a draw whose best cards can still lose is exactly how tainted outs quietly bleed away a stack.
Eight outs looked like a call, but two of them could hand an opponent a flush, so your real equity was closer to six outs' worth - and six outs folds where eight would call. Count clean outs, not gross ones.

Discount outs that could make you the second-best hand - cards that also fill a flush or pair the board - and decide on your effective outs, not the gross count.