 Hello and welcome to the session. In this session we will discuss sets and methods to represent sets. First we shall define what is a set. A set is a well defined collection of objects. The objects in a set should be clearly distinguishable. Let us now learn about collections which are sets. Let us take some examples. The first example is the collection of unique letters in the word soccer. Now the unique letters in the word soccer are S O C E R. Clearly it is well defined so it is a set. Another example can be the collection of distinct animals found in Delhi Zoo. Now this collection is also well defined so it is a set. Now see a collection which is not a set. One example can be the collection of vegetables which tastes good. Clearly it is not a set because what tastes good can vary from person to person. The members of a set are called its elements. Let us now see the notation of a set and its elements. A set is usually denoted by capital letters A, B, C, D and so on. And the members of the set that is the elements are denoted by small letters A, B, C, D and so on. Now if we want to say that an element X is in set S then we say X belongs to S and we write it as X belongs to S. If we want to say that an element X is not in set S then we say X does not belong to S and we write it as X does not belong to S. Now we shall discuss different methods to represent set. First method that we are going to discuss is description method. Second method is tabulation or roster method and the third method is rule method or set builder method. In description method we write the description of the members of the set that states the common property of the elements contained in the set. In description method a set is described in words by stating the common property of all the elements contained in the set. In tabulation or roster method we list the elements of the set and separate them by commas and this list of elements is enclosed in races. Repetition is not done and order of elements is unimportant. So in tabulation or roster method all the elements of the set are listed and closed within races separated by commas. In rule method or set builder method we write a variable say X which represents any member of the set. We then put a vertical a colon and then state the property which all members of the set represent. Let us take an example now. Represent the set of odd numbers from 1 to 10 by all the three methods. In description method we write a is the set of odd numbers from 1 to 10. In tabulation or the roster method we write a is equal to the set containing the elements 1, 3, 5, 7, 9. In rule method or set builder method we write a is equal to the set containing X such that X is an odd number where 1 is less than equal to X is less than equal to 10. With this we end our session. Hope you enjoyed the session.