## Multinomial coefficient :

The multinomial coefficient is a mathematical concept that is used to represent the number of ways in which objects can be arranged into groups. It is commonly used in combinatorics, the branch of mathematics that deals with the study of counting and arranging objects.

For example, suppose we have three different objects, A, B, and C, and we want to arrange them into groups of size 2, 3, and 4, respectively. The number of ways in which we can do this is given by the multinomial coefficient, which is written as:

(2, 3, 4) = (2+3+4)!/2!3!4!

In this case, the multinomial coefficient tells us that there are 1260 ways in which we can arrange the three objects into groups of size 2, 3, and 4.

Another example of the use of the multinomial coefficient is in probability. Suppose we have a bag containing 5 red balls, 6 green balls, and 7 blue balls. We want to determine the probability of selecting 3 red balls, 4 green balls, and 5 blue balls from the bag, without replacement. This probability is given by the multinomial coefficient, which is written as:

(3, 4, 5) = (5+6+7)!/5!6!7!

In this case, the multinomial coefficient tells us that the probability of selecting 3 red balls, 4 green balls, and 5 blue balls from the bag is 0.00217, or about 0.22%.

In general, the multinomial coefficient is used to represent the number of ways in which objects can be arranged into groups, and it is often used in combinatorics and probability to determine the likelihood of different arrangements or combinations of objects. It is a useful tool for calculating the number of possibilities in a given situation, and can be applied to a wide range of problems in mathematics and statistics.