> don't we typically use (15 - 6) here though, instead of ( -8)? > 51%
> actually the 15-6 was (15 - (15-9))
Sorry mate, but this still doesn't make sense. I get the 15-9, that's #outs minus 9 which is 6. But 15 - 6 makes no sense, unless you mean 15*4-6?
> does it work just as well when using the 2 rule?
Well, there isn't a similar system for a Rule of 2 which is just muliplying the outs by 2. However, I did some searching, and there was a site mentioning an improvement by adding 1 if #outs is more than 6, however, I found that to be inaccurate still.
Here's what I've got (check out the attachment). The formula there was:
=IF(A2>9,(A2 * 2) + 2,IF(A2>3,(A2*2)+1,A2 * 2))
Basically means if number of outs is more than 3, add 1, if it's more than 9, add 2.
It's not perfect, but it irons things out a little. Towards 19-21 outs you're losing a whole 1 percent, but that's probably less important if you have shed load of outs; the calculation is a little more useful with less outs. No one needs such precise calculations anyway. You also have to bear in mind 1 fact when using Rule of 2, the percentage is slightly different on the flop and turn (because of less cards remaining on the turn), and that's nearly 1 percent towards the middle range of outs, so losing one percent here and there is OK because you're never going to remember the percentage for the flop and the turn.
With Solomon's Rule of 9, it is pretty straight forward, and because with the standard Rule of 4 the error is growing as you get more outs, Solomon's rule is actually necessary (without it you'll get 84% with 21 outs instead of 70%) whereas with this Rule of 2 modification, it's more work for less gain.
I think people will stick with the good old Rule of 2 and be done with it. It's a rough estimation and more than necessary. My pot odds
calculations are a lot less accurate anyway.
Incidentally, I heard someone say at the casino the other day that 1 card = 2% (because of 50 cards in the deck), and I never thought of the connection with Rule of 2, how rough and nasty it is :-) But knowing this might help work out your outs % pre-flop, rough and nasty again though, e.g. hitting my set on the flop: 2 outs, 3 flop cards with each card being 2%, 2*3*2=12% to hit a set (after writing this I'll see if there's a dirty Solomon's rule for calculating outs preflop heh).
*sigh* enough of this....time to play some poker!