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Sets — Maths STD 11 Science — Question

CBSE BoardEnglish MediumSTD 11 ScienceMathsSets1 Mark
MCQ
Let $\ce{n(A) = 28, n(A ∩ B) = 8, n(A ∪ B)} = 52,$ then $\ce{n(A ∩ B′)} =.$
  • A
    $30$
  • B
    $32$
  • ✓
    $20$
  • D
    none of these.
✓

Answer

Correct option: C.
$20$
Given $\ce{n(A) = 28, n(A ∩ B)} = 8.$
We have $\ce{A ∩ B′ = A − A ∩ B.}$
This give $\ce{n(A ∩ B′) = n(A) − n(A ∩ B)}$
or, $\ce{n(A ∩ B′)} = 28 − 8 = 20.$

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