two to come odds

Why are there different percentage figures on pages 105 and 112 within Petriv's odds book. By this I mean, why is it on page 105 it is approximately 31 and 35 % for 9 outs and on page 112 it is listed as 19 and 20% for the same 9 outs with two to come? The two tables contradict one another; but I'm sure there's a good explanation out there. It would seem the 19 and 20 % is more acurate, but the 31 and 35% is more widely used in other books.

Anyone know how to give a layman's explanation on this one?

Thanks in advance.


p.s.

please post response in probability forum where this was first posted today.

I don't have the book.


But with 9 cards you want and 47 unseen card resulting in 38 bad cards, your chances of making the flush on the next card is 38:9 4.2:1 against; or 81% you miss or 19% you hit.


With 2-cards to go its a little trickier. The chance to MISS on the next card is 38/47 and if you do miss, the chances that you miss on the river is 37/46, so the chances you miss on both cards is 38/47*37/46 = 65%, resulting in 35% of the time you make it, or 1.86:1 against.


Either the table on 112 is mislabeled or you have misread it.


- Louie