n choose r formula (nCr or C(n,r) formula) is used to find the number of combinations or ways to choose r items from a set of n distinct objects. The n choose r formula is given by nCr = n! / r!(n - r)!.
A combination is a selection of items from a set in which the order of the items does not matter. The formula for the number of combinations of n items taken r at a time is: C(n, r) = n! / (r! * (n-r)!)
A combination is a selection of items from a set in which the order of the items does not matter. Combinations are used to count the number of ways to select a subset of items from a set.