Question

if A and are 2disjoint sets that n(a)=24, n(b)=22. find n(a union b)and n(a-b).​

Answer 1

Answer:

Since A and B are disjoint sets it is obvious that no element of A is repeated in B.

n(A) will represent the number of elements in A. and n(B) will represent the number of elements in B. Union in set theory means the combination of elements of A and B but without repetition. Hence n(A union B) represents the number of elements in the union set. Since they both are disjoint sets and have no elements in common the number of elements in the union set will be the sum of the number of elements in A and number of elements in B.

using formula it can be explained as follows:

n(A U B)= n(A)+ n(B)- n(A intersection B).

since n(A intersection B) is 0 the formula can be reduced as

n(A U B)= n(A)+ n(B)- 0

which is same as

n(A U B)=n(A)+ n(B)