Playing 9 vs. 7 in Blackjack

Here's the situation:

You're playing in a multiple deck game that will allow you to double down on any two cards. You have been dealt a four and a five for a two-card nine with the dealer showing a seven as his upcard. You know you have something of an advantage here. The question is how far you want to press it. Your decision, essentially, is whether to just hit this hand or to take a shot at doubling it. What option do you exercise?

The correct play is to hit the hand, rather than double.

A hand of 9 is often a good one to double on. we want to do it when the dealer has weak upcards. But we don't want to do it here. Remember, the seven is an upcard that will make the dealer "pat" (possessor of a standing hand) a little under 74% of the time. He will bust at slightly less than a 26% rate with it, and will make 19 or better in 23% of all situations.

If you wind up doubling here, you'll win more then you lose, no question, but even with the double value of your units factored in, does it present more of an overall win than hitting?

When you hit the nine against the seven, you'll win a little more than 54% of the time and lose 35.7%. There's a healthy winning margin which comes out to 18.6%. In fact, your winning expectation relative to the number of hands played is almost doubled when you hit, as opposed to doubling down.

US vs. THEM Blackjack Strategy Series
An Analysis
By Charles Jay

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