Sets

Question 0

What are items in a set called?

Answer 0

They’re called elements
E.g {1,2,3,4,5}
|| The elements in the set are 1,2,3,4,5,-
Positive whole numbers / Natural numbers

Question 1

What are sets?
Or what is a set?
Give an example…

Answer 1

A set is a collection of well defined objects

E.g G= { T,T,S,S,Y,Y,H,J} member of Girls’ Generation

Question 2

“6 is an element of A”
“7 is not an element of B”
Define the meaning of this sentence

Answer 2

It means 6 is an element of A
6 is in set A
6 € A

5 is not an element of Set B
5 is not in set
5 €/ B

Question 3

What’s a cardinal number?

Answer 3

The number of elements in a set.
A= { 1,2,3,4,5}
#= 5

Question 4

What would be the symbol for an empty / null set?

Answer 4

{} or o/

Question 5

When all elements in Set X are exactly the same in set Y,
What would we call this set?
And how would we symbolise this?

Answer 5

Equal sets

E.g Y= { colours of the Ireland flag}
X= {Green,white,orange}

X=Y

Question 6

If X and Y are equivalent when set A has the same number of elements as Set B, What would these sets be called?

How would this be shown/symbolise?

Answer 6

These are called Equivalent Sets

E.g X= {2,4,6,8}
Y={a,b,c,d}
#X=4   #Y=4

We then say A~B

Question 7

What are proper subsets?

Give examples…

Answer 7

Proper subsets= Subsets that contain AT LEAST one element of the bigger set but not all the elements.

E.g
X={1,2,3,4,5}
Y={1,2}

Question 8

What are subsets?

Give an example…

Answer 8

A set in a set

E.g A= {3,6}
B= {3,6,9}
C={3,10}

A c B reads “A is a subset of B”
A c/ B reads “ A is not a subset of B”

Question 9

What are improper subsets!

Answer 9

c c/

improper subset= Every set is an (IMPROPER) subset of itself.The null set is an (IMPROPER) subsetof all sets.

Improper Subset of A (previous question)
{1,2,3,4} and { }

Question 10

What’s a universal set?

Answer 10

U - All the elements in both set and the ones on the outside
-> ( Venn diagram)

Question 11

What does Y u X means?

Answer 11

It means X union Y

Is what in both Set X and Y

Question 12

What does X n Y means?

Answer 12

X n F -> IntersectioN

Elements found IN BOTH SET

Question 13

In a class of 28 students ,11 students study home ec.,9 study Woodwork and 2 study both.

Work out the solution for this problem.

Answer 13

Home Ec. 11 - 2 = 9
Woodwork 9 - 2 =7

9+2+7 = 18
28-10=18

Question 14

What are natural numbers?

Answer 14

Natural numbers are positive whole numbers

E.g N= 1,2,3,4,5,6,7……….

Question 15

Name an even number that isn’t a natural number

Answer 15

0- Zero