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Given the sets [tex]\( A = \{\text{multiples of 3 less than 12}\}, B = \{\text{integers between 4 and 8}\} \)[/tex], and [tex]\( C = \{4, 5, 7\} \)[/tex], find:

(i) [tex]\( A \cap B \)[/tex]

(ii) [tex]\( (A \cup B) \cap C \)[/tex]

(iii) [tex]\( (A \cap B) \cup C \)[/tex]


Sagot :

Let's solve the given problem step-by-step involving the operations on sets [tex]\(A\)[/tex], [tex]\(B\)[/tex], and [tex]\(C\)[/tex].

First, we need to clearly define the sets:

- [tex]\( A = \{ \text{multiples of 3 less than 12} \} = \{3, 6, 9\} \)[/tex]
- [tex]\( B = \{ \text{integers between 4 and 8} \} = \{5, 6, 7\} \)[/tex]
- [tex]\( C = \{4, 5, 7\} \)[/tex]

With these sets defined, let's proceed with the parts of the problem.

(i) [tex]\( A \cap B \)[/tex]

The intersection of two sets includes all elements that are present in both sets. Here we need to find the common elements between [tex]\(A\)[/tex] and [tex]\(B\)[/tex].

- [tex]\(A = \{3, 6, 9\}\)[/tex]
- [tex]\(B = \{5, 6, 7\}\)[/tex]

The common element between these sets is [tex]\(6\)[/tex].

So,
[tex]\[ A \cap B = \{6\} \][/tex]

(ii) [tex]\( (A \cup B) \cap C \)[/tex]

First, we need to find the union of sets [tex]\(A\)[/tex] and [tex]\(B\)[/tex], then we will find the intersection of the resulting set with [tex]\(C\)[/tex].

- [tex]\(A = \{3, 6, 9\}\)[/tex]
- [tex]\(B = \{5, 6, 7\}\)[/tex]

The union of [tex]\(A\)[/tex] and [tex]\(B\)[/tex] is all elements that are in either [tex]\(A\)[/tex] or [tex]\(B\)[/tex]:

[tex]\[ A \cup B = \{3, 6, 9, 5, 7\} \][/tex]

Next, we find the intersection of this union with [tex]\(C\)[/tex]:

- [tex]\(A \cup B = \{3, 6, 9, 5, 7\}\)[/tex]
- [tex]\(C = \{4, 5, 7\}\)[/tex]

The common elements here are [tex]\(5\)[/tex] and [tex]\(7\)[/tex].

So,
[tex]\[ (A \cup B) \cap C = \{5, 7\} \][/tex]

(iii) [tex]\( (A \cap B) \cup C \)[/tex]

First, we already found the intersection [tex]\(A \cap B\)[/tex] in part (i):

[tex]\[ A \cap B = \{6\} \][/tex]

Next, we form the union of this intersection with set [tex]\(C\)[/tex]:

- [tex]\(A \cap B = \{6\}\)[/tex]
- [tex]\(C = \{4, 5, 7\}\)[/tex]

The union is all elements that are in either [tex]\(\{6\}\)[/tex] or [tex]\(\{4, 5, 7\}\)[/tex]:

[tex]\[ (A \cap B) \cup C = \{4, 5, 6, 7\} \][/tex]

Finally, let's summarize the results:

(i) [tex]\( A \cap B = \{6\} \)[/tex]

(ii) [tex]\( (A \cup B) \cap C = \{5, 7\} \)[/tex]

(iii) [tex]\( (A \cap B) \cup C = \{4, 5, 6, 7\} \)[/tex]