Calculating the house percentage on each kind of keno ticket is a long and complex process. If first involves calculating the odds of hitting every possible payoff combination for that ticket. This must be multiplied against all the payoffs offered by the house for this ticket. Finally, it is necessary to calculate how much it would cost to play every possible ticket of that particular type (for example, all possible eight-spot tickets), and this cost must be compared to the previously calculated payoff total. This process has to be repeated for each of the fifteen possible straight tickets. Finally, since each casino has its own payoff schedule, this process would have to be repeated at each casino you play in. It's not exactly the kind of thing you work out in your head while filling out your ticket in the keno lounge.
Those who have taken the trouble to perform these calculations (with the help of computers) have all agreed that, as so often happens in gambling, the variety offered by different kinds of keno tickets and different payoff schedules is more apparent than real. All keno tickets in virtually all casinos have a house percentage of just around 25 percent. To put this in perspective, this is about five times as high as the percentage one faces when he makes a bet at the roulette table and about eighteen times as high as the percentage on a line bet at craps. Admittedly, the player would make many bets at roulette or craps in the time it would take to play one keno ticket. This means that the percentage at those other games are applied repeatedly far more often, which gives them that much more opportunity to grind down the player's bankroll. This does not change the fact that a 25 percent edge makes keno as bad a game as one will encounter in a casino.
That 25 percent figure is the most important thing you must always remember about keno. It is far more relevant to you chances of success than all the esoterica about exotic combination tickets. It makes it clear that the best strategy one can ever hope to fashion for keno is to stay away from the game. The next-best strategy is to risk as little money at it as possible. If you feel you have to play the game at all, you should stick to small wagers. Fortunately, the low minimums at the game make this possible.
The answer to the often-asked question, what are the best numbers to bet on, is: it doesn't matter. Every number has the same chance of coming up as every other number. If you don't buy that claim, go back and read the section on the fallacy of the maturity of chances. Add to what we have already learned about the mnemonic powers of dice and roulette wheels the following, simple but profound truth: ping-pong, balls have no memory.