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Thread: 10-liner: Five-card charlie 21strategy deviations and a return check

  1. #1
    10-liner
    Guest

    10-liner: Five-card charlie 21strategy deviations and a return check

    Rules:

    8 deck
    S17
    D9 (actually D8, but that's irrelevant)
    DAS
    Suited BJ pays 2:1
    Five card 21 (not just any five-card non-busted hand) pays 2:1

    This is a game in the Betfair "zero margin" series.

    1) what is the precise return with perfect play? The claim is 100% exactly, but I can find no corroboration for this.

    2) Does the "five card 21 pays 2:1" necessitate any strategy variations? My feeling is that it doesn't but would like confirmation. It is EXACTLY 21 required, and only five cards, not six or more or any five-card charlie.

  2. #2
    10-liner
    Guest

    10-liner: Re: Five-card charlie 21strategy deviations and a return check

    You also cannot split aces.

    8 deck
    S17
    D9 (actually D8, but that's irrelevant)
    DAS
    AA cannot be split
    Suited BJ pays 2:1
    Five card 21 (not just any five-card non-busted hand) pays 2:1

  3. #3
    Don Schlesinger
    Guest

    Don Schlesinger: Re: Five-card charlie 21strategy deviations and a return check

    > Rules:

    > 8 deck -0.573%
    > S17 0
    > D9 (actually D8, but that's irrelevant) -0.087%
    > DAS +0.142% (probably slightly less, since D9)
    > Suited BJ pays 2:1 +0.566%
    > Five card 21 (not just any five-card non-busted hand)
    > pays 2:1 +0.2% (estimate from Wong's "Pro BJ," p. 85)

    Grand total: +0.248.

    > This is a game in the Betfair "zero margin"
    > series.

    Appears too good to be true. So, they probably cheat! :-)

    > 1) what is the precise return with perfect play?

    See above.

    > The claim is 100% exactly, but I can find no corroboration
    > for this.

    They're being modest. :-)

    > 2) Does the "five card 21 pays 2:1"
    > necessitate any strategy variations?

    Yes, but very few. See Wong, p. 96.

    > My feeling is
    > that it doesn't but would like confirmation. It is
    > EXACTLY 21 required, and only five cards, not six or
    > more or any five-card charlie.

    A few hands are hit that otherwise wouldn't be. Can't add very much.

    Don

  4. #4
    10-liner
    Guest

    10-liner: Re: Five-card charlie 21strategy deviations and a return check

    Thanks.

    Actually, D8 isn't totally irrelevant - I forgot that A7 qualifies as "8", so A7 v. 3 - 6 can double. That offsets the no split for AA quite a bit.

    Still seems over 100% though. I make AA hit only about -0.17, and the A7 doubles about +0.11 or so.

  5. #5
    10-liner
    Guest

    10-liner: Re: Five-card charlie 21strategy deviations and a return check

    This appears to be the full tally:

    8 deck -0.573%
    S17 0
    D9 -0.087%
    DAS +0.142% (probably slightly less, since D9)
    Suited BJ pays 2:1 +0.566%
    Five card 21 pays 2:1 +0.2%

    Total: +0.248.

    Then:

    -0.176 for no ace split

    Total: +0.0717

    +0.0273 for A7 v 3, 4, 5, and 6 double not hit.

    Grand total +0.099

    I've taken the double and AA figures from a combination of the EV tables at BJmath and Don's "frequency" charts in BJA.

    They claim 100% exactly. Something is wrong somewhere.

    Could the 0.2% on five card 21 possibly be an overestimate?

  6. #6
    MGP
    Guest

    MGP: Re: Five-card charlie 21strategy deviations and a return check

    > Rules:

    > 8 deck
    > S17
    > D9 (actually D8, but that's irrelevant)
    > DAS
    > Suited BJ pays 2:1
    > Five card 21 (not just any five-card non-busted hand)
    > pays 2:1

    > This is a game in the Betfair "zero margin"
    > series.

    > 1) what is the precise return with perfect play? The
    > claim is 100% exactly, but I can find no corroboration
    > for this.

    > 2) Does the "five card 21 pays 2:1"
    > necessitate any strategy variations? My feeling is
    > that it doesn't but would like confirmation. It is
    > EXACTLY 21 required, and only five cards, not six or
    > more or any five-card charlie.

    I assumed SPL3 as well.

    The EV's are:
    TD: 0.21050738242957%
    CD: 0.219422756294933%

    There are a few 4-card exceptions but their not worth typing out for 0.009%

    These are not estimates - they should be exact top-of-the-deck values.

    Sincerely,
    MGP

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