Whenever there is a selection of some elements from a certain group, there are several ways to do so. There are different combinations from the group which can be selected. The concept of combination means that there are certain number of elements to be selected from the group and there is no importance given to the order of the selection. The total number of students are 20, and 4 out of them have to be selected. It can be clearly seen that the order of selection does not matter, therefore the formula to be used is:
