Q. When is the right time to double for less? I was at a $10 blackjack table, and there was one big player, betting $50 or $100 a hand. Sometimes when he had a $100 bet, he'd double down for $50 instead of $100.

I noticed he was mostly doing it when the dealer had a 7, 8 or 9 face up. I suppose he figured the dealer was less likely to bust with those cards, so he didn't want to risk losing as much if he didn't draw a good card. Is that a good rule of thumb, double for less when the dealer doesn't have a bust card?

A. I've never doubled for less. I suppose I'd double for less if I didn't have enough left in my day's gambling budget to double for the full amount. But really, I don't let it get to that point. If I can't afford a full double down, I'm done playing.

Basic strategy players double down when they have an advantage. In every situation where the basic strategy card calls for you to double, you have a better than 50 percent chance of winning the hand. When that happens, you want to press your advantage, and that means doubling for the full amount. Heck, if casinos were to allow you to triple down or quadruple down, you'd want to do that anytime you have an edge.

Double downs are among the options casinos give players to keep the house edge from being so high no one would want to play. The house edge comes from the 8 percent of hands where both the dealer and the player busts. Those hands are won by the house, since the player busts first and the dealer takes away the bet before finishing his or her hand.

That 8 percent edge is reduced to 5.7 percent when the house pays 3-2 on blackjacks - don't play if blackjacks pay only 6-5. Players have the opportunity to take back much of the rest of that edge if they learn basic strategy for hitting, standing, splitting pairs and doubling down. We can get the house edge down to half a percent or so in a six-deck game, a few tenths more or less depending on house rules. But to get there, we have to take full advantage of our options, and that includes doubling down for the full amount.

Q. Whenever I hit a big slot jackpot and get paid by an attendant, they ask me to play it off. It's no big deal. I just won a bunch of money so making one more bet is OK with me.

My question is why they ask in the first place, and what would happen if I refused?

A. The concern is that if a jackpot combination is left on the screen or reels, it will discourage others from playing. Some players believe that if there's a big payoff, the machine goes cold afterward, going into makeup mode until the game earns back the jackpot amount. That's not how slot games work, but the belief is widespread.

If you refused to play once more to get the jackpot combination off the screen, the most likely scenario is that a slot supervisor, in the presence of another casino employee, would use casino money to make the play.

In some jurisdictions, regulations require the extra spin. In the early days of video slots, when coins were still dropping instead of ticket payoffs, extra spins even were required on hand-pays of ordinary cashouts. I once played a nickel video slot and started by putting $50 in the machine - 1,000 five-cent credits. I had my ups and downs, but finally hit the cashout button with 1,020 credits, or $51.

In this casino, policy was to hand-pay any cashout of 1,000 coins or more to limit the need for hopper fills. My last play was a loser, so there was no winning combination on the screen. Nevertheless, the attendant asked me to play it off. I declined, explaining this wasn't a big winner, that I'd about broken even. So with a security guard watching, she opened the machine, took out a nickel token, closed the machine, dropped the token in the slot and gave it one more spin.

I later asked the casino marketing director about the move, and was told state regulation required the spin-off on any handpay, a regulation that was changed a couple of months later.

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