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📐 Mathematics  ·  Sets  ·  JEE

If A and B are disjoint sets, then n(A ∪ B) equals:

Answer: n(A) + n(B).

  • A n(A) + n(B)
  • B n(A) − n(B)
  • C n(A) × n(B)
  • D 0

Correct answer: A. n(A) + n(B)

Explanation: With no overlap, the sizes simply add: n(A ∪ B) = n(A) + n(B).

Set Operations: Union, Intersection, ComplementUABA∩BOutside both circles = (A∪B)' = A'∩B' (De Morgan)A∪B = everything in either circle; A∩B = only the overlap

A Venn diagram makes set identities visual: A∪B is everything inside either circle, A∩B is only the overlap, and the region outside both circles represents the complement of their union - directly illustrating De Morgan's law (A∪B)′ = A′∩B′.

Concept context

Types of sets, operations (union/intersection/complement), relations, and types of functions with domain and range

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