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Let A = {3, 6, 12, 15, 18, 21}, B = {4, 8, 12, 16, 20}, C = {2, 4, 6, 8, 10, 12, 14, 16} and D = {5, 10, 15, 20}. Find B – A.

Answer Verified Verified
Hint: In set theory, the subtraction of a set A from a set B is given by the set obtained by removing all the elements of the set A from the set B. Using this concept, we can solve this question.

Complete step-by-step answer:
Before proceeding with the question, we must know the concept that will be required to solve this question.
Let us assume that we are given two sets A and B. In the set theory, the subtraction of the A from the set B which is denoted by B – A is given by the set obtained by removing all the elements of set A from the set B.


The shaded part in the above venn diagram represents the set B – A.
In this question, we are given set A = {3, 6, 12, 15, 18, 21} and set B = {4, 8, 12, 16, 20}. We are required to find B – A.
We can clearly observe that in set B, the only element which is also present in set A is 12. So, B – A is given by the set obtained after removing the element 12 from the set B.
$\Rightarrow $ B – A = {4, 8, 16, 20}
Hence, the answer is the set {4, 8, 16, 20}.

Note: There is a possibility that one may remove the elements of set B from the set A instead of removing the elements of set A from the set B to find B – A which will give us an incorrect answer.
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