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If n(A−B)=20, n(A∩B)=15, and n(B)=47, find n(B−A).
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Answer and explanation
Correct answer: 32
Set B is divided into two disjoint parts: the elements in B but not A, represented by B−A, and the elements common to A and B, represented by A∩B. Thus n(B)=n(B−A)+n(A∩B). Rearranging gives n(B−A)=47−15=32. The supplied value n(A−B)=20 describes the opposite difference and is not needed.
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What is the correct answer to this question?
32
Why is this the correct answer?
Set B is divided into two disjoint parts: the elements in B but not A, represented by B−A, and the elements common to A and B, represented by A∩B. Thus n(B)=n(B−A)+n(A∩B). Rearranging gives n(B−A)=47−15=32. The supplied value n(A−B)=20 describes the opposite difference and is not needed.
Which subject and chapter does this question cover?
This is a Class 12 Mathematics question. Chapter: Sets.
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