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In mathematics, a combination is a selection of items from a set that has distinct members, such that the order of selection does not matter (unlike permutations).For example, given three fruits, say an apple, an orange and a 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.
A k-combination of a set S is a subset of S with k (distinct) elements. The main purpose of the combinatorial number system is to provide a representation, each by a single number, of all () possible k-combinations of a set S of n elements.
One must divide the number of combinations producing the given result by the total number of possible combinations (for example, () =,,).The numerator equates to the number of ways to select the winning numbers multiplied by the number of ways to select the losing numbers.
The following is an example of an abbreviated wheeling system for a pick-6 lottery with 10 numbers, 4 if 4 guarantee, and the minimum possible number of combinations for that guarantee (20). A template for an abbreviated wheeling system is given as 20 combinations on the numbers from 1 to 10.
Multiple points on a line imply multiple possible combinations (blue). Only lines with n = 1 or 3 have no points (red). In mathematics , the coin problem (also referred to as the Frobenius coin problem or Frobenius problem , after the mathematician Ferdinand Frobenius ) is a mathematical problem that asks for the largest monetary amount that ...
The same argument shows that the number of compositions of n into exactly k parts (a k-composition) is given by the binomial coefficient (). Note that by summing over all possible numbers of parts we recover 2 n−1 as the total number of compositions of n:
In this example, the rule says: multiply 3 by 2, getting 6. The sets {A, B, C} and {X, Y} in this example are disjoint sets, but that is not necessary.The number of ways to choose a member of {A, B, C}, and then to do so again, in effect choosing an ordered pair each of whose components are in {A, B, C}, is 3 × 3 = 9.
Combinations and permutations in the mathematical sense are described in several articles. Described together, in-depth: Twelvefold way; Explained separately in a more accessible way: Combination; Permutation; For meanings outside of mathematics, please see both words’ disambiguation pages: Combination (disambiguation) Permutation ...