Straight-Flush Draw

[BeauKooJack]

I'm a beginner and I was reading "Winning Low Limit Hold'Em" by Lee Jones. He states: "If you flop an open end straight-flush draw (e.g. you have 10s-9s and the flop comes 8s-7s-2c) you are a 1.2:1 favorite to make a straight or better by the river.
Is this correct? As I figure it, out of 47 unseen cards 6 will make a regular straight, 7 will make a regular flush and 2 will make a straight flush. (No Full House or 4 of a Kind). That's 32:15. Good odds but still more than 2 to 1 against improvement. Am I missing something?

[Lost Wages]

Am I missing something?

The 1.2:1 favorite is from the flop to river, i.e. 2 cards to come. One way to figure it is to calculate the probability of missing twice and subtract that from one. If you have 15 outs then you have 32 non-outs on the flop and 31 on the turn. 32/47 * 31/46 = .459 which is the probability of not hitting at least one out. The probability of hitting is then 1-.459 =.541 and the odds are .459/.541:1 = .85:1 against or 1.18:1 in favor.

Lost Wages

[Bulldog]

You are missing the fact that you have TWO chances at that 1 in 3 shot.