Calxsolver
Subject:  Precalculus

Combination

An unordered selection of r objects chosen from n.

The number of combinations nCr = n! / (r!(n − r)!). Combinations count outcomes where the order does not matter — for example, the number of possible five-card poker hands from a deck of 52.

Formula

nCr = n! / (r!(n − r)!)

Used in

Permutations & Combinations Compute nPr, nCr and the factorial. Binomial Expansion Expand (ax + b)ⁿ with the binomial theorem.

See also

Permutation An ordered arrangement of r objects chosen from n. Factorial The product of all positive integers from 1 up to n, written n!. Binomial theorem A formula that expands (a + b)ⁿ as a sum of terms with binomial coefficients.