CombinationIt is a mathematical technique that determines the possible arrangements in a collection of items where the order of the selection does not matter. In combination, you can select items in any order.The number of combinations of set n distinct object taken by r at a timenCr = n! / (r! (n-r)!)n C r = number of combinationsn = total number of objects in the setr = number of choosing objects from the setfor exampleselect four fruits out of ten fruits.n = 5r = 2nCr = 5! / (5-2)!4!= 10! / 6!4!= 210so the combination of 4 fruits out of 10 fruits is 210