Page 7 - Math 7

Unit Set
1

1.1 Set – Looking back

Classroom - Exercise

1. Let's write any three members of the well defined collections inside braces.
a) A collection of High mountains of Nepal ....................................................
b) A collection of mountains of Nepal which have more than 6000 m altitude.
.........................................................................................................................

c) A collection of fruits. .....................................................................................
d) A collection of tasty fruits. ............................................................................

2. If W = {0, 1, 2, 3, 4, 5} and A = {2, 4, 6}, let's tell and write 'true' or 'false'.
a) A  W = ................. b) 2  W = .................
c) 6  W = ................. d) {2, 4}  W = .................

3. Let's tell and list the elements of these sets.
a) {letters of the word ‘SUCCESS’} ...................................................................
b) {x : x <10, x  odd number} .......................................................................

4. The set-builder form of A = {2, 4, 6, 8} .............................................................

It is a collection of whole numbers less than 5. Then, it
0 definitely includes the numbers 0, 1, 2, 3 and, 4. Because the
1 2
statement ‘whole numbers less than 5’ defines the distinct and
3 4 distinguishable objects which are to be included in the collection.
Therefore, it is a well-defined collection and it is called a set.

On the other hand, is it possible to write the members of the collection
of tall students of your class? Is it possible to write the members of
the collection of tasty fruits? Discuss why these collection are not the
well - defined. Therefore, the collections which are not well-defined are not sets.

1.2 Membership of a set and set notation

A member or an element of a set is any one of the distinct objects that make up that
set.

For example, in a set N = {1, 2, 3, 4, 5} , the members or elements of the set N are
1, 2, 3, 4, and 5.

Approved by Curriculum Development Centre, Sanothimi, Bhaktapur 5 Vedanta Excel in Mathematics - Book 7