Question

1. A = {1,2} B {3,4,5,6} then n(A)+n(B) = ?

Answer 1

Answer:

25

equal to

0

A null set is a set which has no elements in it. So, the cardinal number of a null set is zero.

Answer 2

Explanation:-

★(i).

A = { 1,2}

⇛ n (A ) = 2

B = { 3,4,5,6}

⇛ n (B) = 4

n(A)+n(B) = 2+4 = 6

★(ii).

The symbol ⇛ means Implies

★(iii).

A = Phi = {}

B = phi = {}

AUB = { } U { } = { }

AUB = phi = { }

(iv).

AUB = BUA is called Commutative law in sets uner union .

★(v).

Null set = Void set = Empty set = { }

Number of elements in the empty set = 0

⇛ Cardinal number of null set is zero (0)

★(vi). If AUB = B then B is the super set and A is the sub set of B

★(vii). A = { 1,2,3,4}

B = {2,4,6,8}

A-B = {1,2,3,4} - { 2,4,6,8}

=> A-B = { 1,3}

★(viii). n(AUB) = 8

n(A) = 6

n(B) = 4

We know that

n(AnB) = n(A)+n(B)-n(AUB)

⇛ n(AnB) = 6+4-8

⇛n(AnB) = 10-8

⇛ n(AnB) = 2

or n(AUB)+n(AnB) = n(A)+n(B)

⇛ 8+ n(AnB) = 6+4

⇛ 8+ n(AnB) =10

⇛ n(AnB) = 10-8

⇛ n(AnB) = 2

Therefore, n(AnB) = 2