?? Did I just notice a flaw in the blackjack strategy charts ??

[bryan_in oregon]

Why do blackjack strategy charts say when the dealer has a 4 up to hit an A,2 / A,3 but to double down on A,4 / A,5? Because A,2 thru A,5 all have 5 cards that would make the hand 17 or higher
A,2,3,4,5,6,7,8,9 and 10s*4 = 13 card possibilities that could be dealt to you when taking a card

A,2 (4,5,6,7,8) 5 out of 13 = 38.46% of the time you will get 17-21 w/1card

A,3 (3,4,5,6,7) 5 out of 13 = 38.46% of the time you will get 17-21 w/1card

A,4 (2,3,4,5,6) 5 out of 13 = 38.46% of the time you will get 17-21 w/1card

A,5 (A,2,3,4,5) 5 out of 13 = 38.46% of the time you will get 17-21 w/1card

So if your chances of getting an 17-21 are exactly the same, why when the dealers up card is an 4 are the rules different for doubling down on A,2 - A,5 it should be "hit" on A,2 - A,5 or "Double" on A,2 - A,5 because there is no difference when it come to doubling. Can someone tell me why this is? or did I just notice a flaw in the blackjack strategy charts.

 

[ScottH]

Why do blackjack strategy charts say when the dealer has a 4 up to hit an A,2 / A,3 but to double down on A,4 / A,5? Because A,2 thru A,5 all have 5 cards that would make the hand 17 or higher
A,2,3,4,5,6,7,8,9 and 10s*4 = 13 card possibilities that could be dealt to you when taking a card

A,2 (5,6,7,8,9) 5 out of 13 = 38.46% of the time you will get 17-21 w/1card

A,3 (4,5,6,7,8) 5 out of 13 = 38.46% of the time you will get 17-21 w/1card

A,4 (3,4,5,6,7) 5 out of 13 = 38.46% of the time you will get 17-21 w/1card

A,5 (2,3,4,5,6) 5 out of 13 = 38.46% of the time you will get 17-21 w/1card

So if your chances of getting an 17-21 are exactly the same, why when the dealers up card is an 4 are the rules different for doubling down on A,2 - A,5 it should be "hit" on A,2 - A,5 or "Double" on A,2 - A,5 because there is no difference when it come to doubling. Can someone tell me why this is? or did I just notice a flaw in the blackjack strategy charts.

Not all dealer cards are equal. In your calculations you didn't take into account the different dealer upcard. The dealer will make a pat hand more often with a 4 compared to a 5 or 6. The higher bust frequency with a 5 or 6 showing justifies doubling with the A2 or A3. But the 4 is a little bit stronger of a dealer upcard, so you don't double your A2 and A3.

Like Ken Smith likes to say, the real reason is just because that's what the calculations say. But that is my best attempt at a normal explanation.

 

[ScottH]

A,2 (5,6,7,8,9) 5 out of 13 = 38.46% of the time you will get 17-21 w/1card

A,3 (4,5,6,7,8) 5 out of 13 = 38.46% of the time you will get 17-21 w/1card

A,4 (3,4,5,6,7) 5 out of 13 = 38.46% of the time you will get 17-21 w/1card

A,5 (2,3,4,5,6) 5 out of 13 = 38.46% of the time you will get 17-21 w/1card

Alhough it doesn't change your calculations it actually should be

A,2 (4,5,6,7,8)
A,3 (3,4,5,6,7)

etc.

 

[KenSmith]

Let's compare doubling A2 vs 5 and doubling A5 vs 5.
As Bryan points out, we have the same chances of ending up with 17,18,29,20,21.

However, doubling A2 "costs" more than doubling A5...
With A2, there are 4 cards you can draw that you'd like to be able to hit again, but aren't allowed.
With A5, there is only one card you can draw that you'd like to be able to hit again. (The Ace).

 

[QFIT]

You aren't taking into account the possibility of drawing multiple cards. The problem with doubling is that you only get one card. If it's a bad draw, you don't get a second chance. With A5v4 you will very rarely hit multiple times. (Only when drawing an Ace.) With A2v4 you are much more likely to hit twice. Therefore, doubling (which doesn't allow multiple hits) is less problematic with A5v4.

 

[QFIT]

Ken beat me to it

 

[bryan_in oregon]

I'm only talking about a dealer up card of a 4

(Thanks SchottH I fixed the mistake in the original post).

and Thanks "KenSmith" you make a good point.

 

[Canceler]

Seen it so many times!

You aren't taking into account the possibility of drawing multiple cards.

I would guess this is the number one cause of threads of this type.