Many more than four reel symbols are actually used.

Random number generators work from much larger number sets, leading to exponentially greater possibilities.

Modern slot machine or online slots odds work in much the same way, except that the math is more complex for several reasons: By paying less than the true odds of the game, the machine has a payback percentage of 83.2 percent, or a little less than today’s 1- cent games. Multiplied by the frequency of wins, those payoffs total 832 coins. So instead it pays 160 on three 7s, 25 on three bars, 8 on three cherries and 4 on three watermelons. But the casino must have an edge, or it couldn’t pay the bills and offer the game. One way to do that would be to have payoffs of 170 coins on three 7s, 30 on three bars, 10 on three cherries and 5 on three watermelons. If the game paid at true odds, then the payoffs would be set up so that each 1,000 coins wagered would bring 1,000 coins in payoffs.

900 of the 1,000 combinations mix different symbols.

Eight combinations will be three bars, 27 will be three cherries and 64 will be three watermelons.

Only one combination – or 1 x 1 x 1 – will be three 7s.

There are 1,000 possible three-reel combinations – 10 symbols times 10 symbols times 10 symbols.

Each reel also has two bars, three cherries and four watermelons.

Each reel has one 7 – that’s the top jackpot symbol. With 100 symbols on each of five reels, there are 10 billion combinations. Most modern video slots have five video reels can be as long as the gamemaker needs them to be. The Megabucks three-reel slot that paid the world record jackpot of more than $39 million has about 50 million combinations. With 100 stops on each of three reels, there are 1 million combinations.

The change to virtual reels enabled programmers to make the reels to behave as if they had any number of stops. With bigger reels holding 20 symbols and 20 spaces, combinations increase to 40x40x40, or 64,000.

If blank spaces between lines are used as stops, the number of combinations increases to 20x20x20, or 8,000.

On early three-reel slots with 10 symbols per reel, there were 1,000 possible combinations (10 x 10 x 10).

The sheer number of possibilities makes the math that goes into slot machine odds more complicated than on table games.

The number of winning combinations and the payoffs per winner work together to determine a game’s odds. There also is an open field for game designers to assign how much each winning combination pays. There are thousands, and sometimes millions, of reel combinations. Slot machine odds work in a similar fashion to the roulette example, except there are many more possibilities on the slots.

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