A shuffle through the Gaming mailbag:

Q. How is payback percentage on a slot machine calculated? I know I’m not really getting zero percent when I lose all my money, but it sure doesn’t feel like 90, either.

A. Payback percentage is all money paid out divided by all wagers, with the result multiplied by 100 to convert to percent.

For example, if players make \$1 million worth of wagers in a machine, and it pays out \$900,000, then you’d divide \$900,000 by \$1 million to get 0.90. Multiply that by 100, and you get 90 percent.

To apply that to an individual player, you have to understand that any payout you receive counts on the payout side, even if you then lose it.

Let’s say you start with \$100 and bet \$1 a spin, and that for the first 100 spins you receive \$90 in payouts. For the next 90 spins, you receive \$80. Then you get a nice hit or two, and the next 80 spins take you back to \$100. After that, you decline \$10 each time — 100 spins for \$90, 90 for \$80, 80 for \$70, 70 for \$60, 60 for \$50, 50 for \$40, 40 for \$30, 30 for \$20, 20 for \$10 and 10 with no return.

At the end, you haven’t made \$100 worth of wagers. You’ve bet \$820. And your return isn’t zero, it’s \$720.

You’d had a payback percentage of (\$720/\$820)*100, or 87.8 percent.

It’s probably no consolation as you walk away having lost your entire \$100, but the machine has paid something close to a normal percentage.

Sometimes we lose money a lot faster than that; sometimes we walk away without losing it all and sometimes we win. The total of all payouts and all wagers by the many who play the games lead to the overall payback percentage.

Q. I went to the sports book and saw the Cubs as a 7-2 first choice to win the World Series. I wanted someone with a better price if I’m going to bet futures, so I took the Astros at 12-1.

But I guess my big question is, should you always just avoid last year’s champion? The last team to repeat was the Yankees in 2000 after they also won in 1998 and 1999.

A. It’s harder for any team to win the postseason than it once was, but that applies to everyone and not just the defending champs.

Leaving aside the issue of just qualifying for the postseason, any playoff team faces an uphill struggle with more rounds of playoffs in the wild-card era.

Baseball’s postseason was just the World Series from 1903 through 1968, with no Series in 1904. The previous champion won 14 of 65 Series, or 21.5 percent.

From 1969 to 1993, playoffs expanded to four teams as the National and American Leagues split to two divisions each. Five of the 25 Series, or 20 percent, were won by the previous champ.

There was no Series in 1994, but starting in 1995, playoffs expanded to eight teams with three division winners and a wild card per league. In 2012, a second wild card per league was added, creating two wild-card games to qualify for the eight-team playoffs.

In 22 years of the wild-card era, there have been only two repeat winners, or 9.1 percent.

Bottom line No. 1 is that it’s harder to win as one of eight or 10 postseason teams than as one of two. Bottom line No. 2 for me is that I avoid futures bets, which have high house edges and involve so much uncertainty.