# Combination

In mathematics a combination is a way of selecting several things out of a larger group, where (unlike permutations) order does not matter. In smaller cases it is possible to count the number of combinations. For example given three fruit, say an apple, orange and pear, there are three combinations of two that can be drawn from this set: an apple and a pear; an apple and an orange; or a pear and an orange. More formally a k-combination of a set S is a subset of k distinct elements of S. If the set has n elements the number of k-combinations is equal to the binomial coefficient

which can be written using factorials as whenever, and which is zero when . The set of all k-combinations of a set S is sometimes denoted by .

Combinations can refer to the combination of n things taken k at a time without or with repetitions. In the above example repetitions were not allowed. If however it was possible to have two of any one kind of fruit there would be 3 more combinations: one with two apples, one with two oranges, and one with two pears.

With large sets, it becomes necessary to use more sophisticated mathematics to find the number of combinations. For example, a poker hand can be described as a 5-combination (k = 5) of cards from a 52 card deck (n = 52). The 5 cards of the hand are all distinct, and the order of cards in the hand does not matter. There are 2,598,960 such combinations, and the chance of drawing any one hand at random is 1 / 2,598,960.

### Other articles related to "combination, combinations":

Probability: Sampling A Random Combination
... are various algorithms to pick out a random combination from a given set or list ... One way to select a k-combination efficiently from a population of size n is to iterate across each element of the population, and at each step pick that element with a dynamically changing probability ...
Secret Combination (Latter Day Saints)
... In the Latter Day Saint movement, a secret combination is a secret society of "people bound together by oaths to carry out the evil purposes of the group." Secret combinations were first ... The most notable example of a secret combination is the Gadianton robbers, a conspiracy throughout much of the Book of Mormon narrative ... to the Joseph Smith Translation of the Bible, Cain also entered a secret combination with Satan and became Master Mahan ...
Artemether/lumefantrine
... The combination artemether/lumefantrine (trade names Coartem and Riamet) is a fixed-dose combination artemisinin-based combination therapy (ACT) indicated for the treatment of acute ... The combination is an effective and well-tolerated malaria treatment, providing high cure rates even in areas of multi-drug resistance ... the first fixed dose artemisinin-based combination therapy to meet the World Health Organization's (WHO) pre-qualification criteria for efficacy, safety and quality ...
Dynamic Capabilities - Processes - Co-specialization
... a firm's assets may become co-specialized, meaning that they are uniquely valuable in combination ... patents and tacit knowledge) of a company provide a synergistic combination of complementary assets ... Such co-specialized assets are therefore more valuable in combination than in isolation ...
Melodrama (Vibe Tribe Album) - Notes and Meanings
... Vinyla Sky is a combination of the phrases Vanilla Sky and vinyl record ... Albert Balbert is a combination of Albert Hofmann and Balbert probably comes from the Hebrew slang word "Balbalot" (tripping) ... Stringadelic is a combination of the phrases strings and psychedelic ...

### Famous quotes containing the word combination:

Just as we need to encourage women to test life’s many options, we need to acknowledge real limits of energy and resources. It would be pointless and cruel to prescribe role combination for every woman at each moment of her life. Life has its seasons. There are moments when a woman ought to invest emotionally in many different roles, and other moments when she may need to conserve her psychological energies.
Faye J. Crosby (20th century)

Only amateurs say that they write for their own amusement. Writing is not an amusing occupation. It is a combination of ditch-digging, mountain-climbing, treadmill and childbirth. Writing may be interesting, absorbing, exhilirating, racking, relieving. But amusing? Never!
Edna Ferber (1887–1968)

We attempt to remember our collective American childhood, the way it was, but what we often remember is a combination of real past, pieces reshaped by bitterness and love, and, of course, the video past—the portrayals of family life on such television programs as “Leave it to Beaver” and “Father Knows Best” and all the rest.
Richard Louv (20th century)