Matchplay math question?
  • What hands should not be doubled if you can only match your orginal bet and not the match play as well. Say you have a $10 match play coupon and you bet $10 if when you doubled down you could only add $10 to your bet and not $20 what hands should you not double down on that you normally would?
    Lets say that splitting only costs you $10 instead of $20 what hands should you split that you normally wouldn't?
    Most likely I think you wouldn't double on hands where you have a good chance of wanting to hit twice.

    For a mathplay would it be better to play roulette with them if the roulette wheel only had one zero instead of playing blackjack? You can only make an even money bet and lose the coupon win or lose.
  • learningtocount said:
    What hands should not be doubled if you can only match your orginal bet and not the match play as well. Say you have a $10 match play coupon and you bet $10 if when you doubled down you could only add $10 to your bet and not $20 what hands should you not double down on that you normally would?
    Lets say that splitting only costs you $10 instead of $20 what hands should you split that you normally wouldn't?
    Most likely I think you wouldn't double on hands where you have a good chance of wanting to hit twice.

    For a mathplay would it be better to play roulette with them if the roulette wheel only had one zero instead of playing blackjack? You can only make an even money bet and lose the coupon win or lose.


    I didn't completely understand what you are asking. If you count, you would double or not double exactly as your BS departure indices indicate. If you don't count, you should double whenever basic strategy says double, regardless of whether you are using a matchplay or not. Treat it as a $10 chip, nothing more nothing less.
  • With the matchplay I was not allowed to match it when doubling. Say I had a $5 bet and a $5 matchplay up I could only double down for $5 instead of $10. If I won the double down I would win $15 if I won the hand I would win $10. If I lost the hand without doubling I would lose $5 if I lost the hand with doubling I would lose $10.
  • learningtocount said:
    With the matchplay I was not allowed to match it when doubling. Say I had a $5 bet and a $5 matchplay up I could only double down for $5 instead of $10. If I won the double down I would win $15 if I won the hand I would win $10. If I lost the hand without doubling I would lose $5 if I lost the hand with doubling I would lose $10.


    If you can't double on the coupon, you would double, pretending the coupon was not on the table, which is another way of saying "double for less, but double for whatever the casino will allow."

    I don't recall seeing that kind of limit on a matchplay, but then again, I honestly can't remember if that issue has ever come up (sorry sir but you can't double the matchplay bet itself). I played several MPs at the Tropicana last month. They had some sort of promo dealing with slots that gave a booklet which included a matchplay as well. We finagled our way into several of those and they greatly increase your EV with no increase in risk at all.
  • Some casinos allow you to double the total amount of the bet including the matchplay,some don't.
    Some will pay only even money on the MP if you get a BJ,others pay 3/2 on the total bet.
    The cheaper casinos are far more numereous.
  • When I wasn't allowed to double for the matchplay as well I just hit my hand and sure enough I wanted to hit again after I got my card. I had an Ace-2 against a 4 a normal double but not a great double so I just hit figuring the ability to redraw would be more important. After I learned I couldn't double the matchplay I put my last coupon on roulette and lost.
  • learningtocount said:
    When I wasn't allowed to double for the matchplay as well I just hit my hand and sure enough I wanted to hit again after I got my card. I had an Ace-2 against a 4 a normal double but not a great double so I just hit figuring the ability to redraw would be more important. After I learned I couldn't double the matchplay I put my last coupon on roulette and lost.


    It is pretty common to double and then wish you could hit again. But it is _still_ the right move when BS says it is. You win more money that way...
  • The basic stragedy assumes that you double for the full amount and give up your right to redraw. The basic stragedy does not assume that you double for half of your bet. Which is essentially what I was restricted to. Giving up the right to redraw might cost you more if you can only double for half of your bet than hitting should become more profitable even on basic stragedy double downs.
    Here is an example of a profitable double but a more profitable hit a 9 vs a 7 will win 53% of the time if you double and 59% of the time if you hit. Why do you win more if you just hit?
    The answer is simple the ability to redraw on your hand.
    Doubling for less gives you the worst of both worlds. Lets take the 9 vs a 7 as are example on a $100 bet if you double down you will win an average of $12 $6 for the orginal $100 and $6 for the second $100.
    If you just hit you will win $18 on the average.
    If you double for $50 you will win $9 on the average. $6 For the first $100 and $3 for the 2nd $50.
  • learningtocount said:
    The basic stragedy assumes that you double for the full amount and give up your right to redraw. The basic stragedy does not assume that you double for half of your bet. Which is essentially what I was restricted to. Giving up the right to redraw might cost you more if you can only double for half of your bet than hitting should become more profitable even on basic stragedy double downs.
    Here is an example of a profitable double but a more profitable hit a 9 vs a 7 will win 53% of the time if you double and 59% of the time if you hit. Why do you win more if you just hit?
    The answer is simple the ability to redraw on your hand.
    Doubling for less gives you the worst of both worlds. Lets take the 9 vs a 7 as are example on a $100 bet if you double down you will win an average of $12 $6 for the orginal $100 and $6 for the second $100.
    If you just hit you will win $18 on the average.
    If you double for $50 you will win $9 on the average. $6 For the first $100 and $3 for the 2nd $50.



    You may or may not be right. The math will "tell the tale".

    Of course, there is a question about doubling 9 vs 7 without a card-counting index. I get the following two values: if I hit 9 vs 7, my EV is .1719. If I double 9 vs 7, my EV is .1043... I choose to make the play that has the highest EV, in this case, always hit no matter what.

    Perhaps you were thinking of 9 vs 6?

    But back to the topic. Doubling for less. First, to determine the expected value (EV) the computation goes like this:

    EV = probability of win or lose * bet. EV is usually expressed with respect to unit = 1.00 since you can then multiply the EV times your bet to convert that to a $ amount.

    So for hitting 9 vs 6, EV = .196. So the probability is that we will win more such hands than we lose, and to be precise we will have a winning percentage of 19.6% or for every 100 hands played, we will win 19.6 hands outright, and the other 80.4 hands will be evenly split between wins and losses, with pushes thrown in as well.

    For doubling 9 vs 6, EV = .3171. But that is based on 2 units of bet out since we are doubling. If you double but put no additional chips out (double for nothing?) your EV would be 1/2 of that. or .16 roughly, which is obviously worse than hitting (no surprise there, you doubled, put no more money out, and also gave up the opportunity to hit.)

    If you double for less, and assuming your unit is $100, you double for $10, then your EV would be .3171 * 1.1 / 2.0 which is a bit better. If you repeat that math, you can find the crossing point where double-for-less and hit have the same EV. And if you double for more than that amount, doubling becomes more profitable until you get to a true double where your bet is 2x and you reach the full .3171 EV.

    So, to answer your question, we'd need to know (a) exactly what 3 cards did you see (your two and the dealer's) and what was your initial bet and what was your max double-for-less (which would exclude the matchplay coupon amount). Then we can decide whether doubling for less or hitting was the right decision...
  • I had an ace-2 against a 4. With the matchplay coupon I had $5 on the hand plus the $5 coupon. So I pushed out $10 to double and it was rejected and they said I could only double for $5 so I took that back and just hit.
    I got a 3 on my first hit so I hit it again and got a 10 I than stood with my 16 and the dealer hit a hand and I lost. But I was glad I had the option to hit again. I think the ev for doubling if I could double for the full amount was .5% better than just hitting.
  • learningtocount said:
    I had an ace-2 against a 4. With the matchplay coupon I had $5 on the hand plus the $5 coupon. So I pushed out $10 to double and it was rejected and they said I could only double for $5 so I took that back and just hit.
    I got a 3 on my first hit so I hit it again and got a 10 I than stood with my 16 and the dealer hit a hand and I lost. But I was glad I had the option to hit again. I think the ev for doubling if I could double for the full amount was .5% better than just hitting.


    Now I'm lost. Basic strategy is to hit A2 vs 4 unless you are counting and remember the playing index of that BS departure which is so rare nobody I know of uses it. Doubling has about 1/2 the EV of hitting that particular hand...
  • I looked up the gains for doubling down and it says that it was a small gain to double on Ace-2 against a 4 but in my situation I'm a 100% sure I made the right play.
  • learningtocount said:
    I looked up the gains for doubling down and it says that it was a small gain to double on Ace-2 against a 4 but in my situation I'm a 100% sure I made the right play.



    Can't be. DD has an ev of +.05. Hit has an EV of +.10. +.10 is bigger than +.05 so you hit that except in high counts.

    Either you looked at the charts wrong, or whatever charts you used are wrong. The wizard's web site has the expected return for every possible hand and playing decision listed.

    In your case, if you double for less, your income will be worse than if you just hit outright, so you made the right decision for the wrong reason as doubling should never have been considered at all.

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