Keno is a lottery-like or bingo-like gambling game played at modern casinos. A traditional live casino keno game uses a circular glass enclosure called a "bubble" containing 80 ping pong-like balls which determine the balldraw result. Each ball is imprinted with a number 1 through 80. During the balldraw, a blower pushes air into the bubble and mixes the balls. A "caller" presses a lever opening a tube, where the balls lift one at a time into a "V" shaped tube called the "rabbit ears". The caller and a "verifier" record each of 20 balls drawn, and the computerized keno system calculates all wagers based on the numbers drawn.
Players wager by marking an "X" over the "spot" choices on a blank keno ticket form with 80 numbered selection boxes (1 to 80). After all players successfully place their wagers, the casino draws 20 balls (numbers) at random. Some casinos automatically call the balldraw at preset timed intervals regardless of whether or not players are waiting to place a wager.
Each casino sets its own series of pay scale choices called "paytables". The player is paid based on how many numbers drawn match the numbers selected on the ticket and according to the paytable selected with regard to the wager amount.. Players will find a wide variation of keno paytables from casino to casino and a large deviation in the house edge set for each of those paytables. Additionally, each casino typically offers many different paytables and specialty keno bets for customers to choose from, each with its own unique house edge. No two casinos' keno paytables are identical. There are several Reno and Las Vegas casinos offering as many as 20 or 30 different paytables from which the player can choose.
Keno payouts are based on how many numbers the player choses and how many numbers are "hit", multiplied by the proportion of the player's original wager to the "base rate" of the paytable. Typically, the more numbers a player chooses and the more numbers hit, the greater the payout, although some paytables pay for hitting a lesser number of spots. For example, it is not uncommon to see casinos paying $500 or even $1,000 for a "catch" of 0 out of 20 on a 20 spot ticket with a $5.00 wager. Payouts vary widely from casino to casino. Most casinos allow paytable wagers of between 1 and 20 numbers, but some limit the choice to only 1 through 10, 12 and 15 numbers, or "spots" as keno aficionados call the numbers selected.
The probability of a player hitting all 20 numbers on a 20 spot ticket is approximately 1 in 3.5 quintillion (1 in 3,535,316,142,212,180,000 to be exact). If every person now alive played one keno game every single second of their lives, there would be about one solid 20 jackpot-winning ticket to date. If all these possible keno tickets were laid end to end, they would span the Milky Way galaxy -- and only one of them would be a winner. Even though it is virtually impossible to hit all 20 numbers on a 20 spot ticket, the same player would typically also get paid for hitting "catches" 0, 1, 2, 3, and 7 through 19 out of 20, often with the 17 through 19 catches paying the same as the solid 20 hit.
"Keno runners" walk around calling, "keno!" and offer to carry players' wagers to the keno booth for processing. The keno runner is handed the wager payment and the "inside ticket" (keno wager forms filled out by the customer) and takes the wager and ticket to the keno counter for processing. The keno runner returns with an "outside" ticket, which is the official wager receipt. It is incumbent on the player to check the ticket for errors before the game balldraw is drawn. Any errors not corrected before the balldraw begins are not normally rectified and the "outside" ticket receipt governs in any disputes.
In modern keno, players are offered the option of playing multi-race keno, which books a keno ticket for a number of sequential keno races up to 1000. The races must always start on the next sequential race to be drawn. When the sequence of wagered games is finished, the player is able to redeem any winnings within the time constraints specified in the casino's rules booklet.
After picking wager numbers, recording them at the keno booth and obtaining the "keno ticket" (official wager receipt), the player watches the balldraw in progress as the spot (number) selections light either on an electronic keno board or on a video monitor. Keno displays are typically found throughout the casino and sometimes even appear on a television channel in casino hotel rooms.