Recreational Math

Mathematical Games

What are betting odds and how are they determined?

Betting odds are usually written in the form r:s, in which r is the “chances for” and s is the “chances against.” This can be stated as: “r to s” or “chances for to chances against”; or “s to r” or “chances against to chances for.” But note that odds of 1:1 are said as “one to one” not “one out of one.” Odds are usually calculated as follows:

Using a 52-card deck as an example, the odds of drawing a king from the deck are 1 in 12—or 4:(52 - 4) = 4:48, which equals 1:12.


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