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Class 10MathematicsSetsOperations on Sets (Union, Intersection, Difference)MediumLevel 10

If A ⊆ B, n(A) = 32, n(B) = 57 and n(U) = 90, then what is n(B − A)?

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Answer and explanation

Correct answer: 25

Because A is a subset of B, every element of A is already included in B. Removing A from B therefore leaves the elements that belong only to B. For finite sets, n(B − A) = n(B) − n(A) = 57 − 32 = 25. The universal-set size is not needed for this calculation, so option A is correct.

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setssubsetsset differencevenn diagramsOperations on Sets (UnionIntersectionDifference)operations on sets union intersection differenceMathematicsClass 10 MCQ

Frequently asked questions

What is the correct answer to this question?

25

Why is this the correct answer?

Because A is a subset of B, every element of A is already included in B. Removing A from B therefore leaves the elements that belong only to B. For finite sets, n(B − A) = n(B) − n(A) = 57 − 32 = 25. The universal-set size is not needed for this calculation, so option A is correct.

Which subject and chapter does this question cover?

This is a Class 10 Mathematics question. Chapter: Sets. Topic: Operations on Sets (Union, Intersection, Difference).

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