यदि \(U={1,2,\ldots,30}\), (A) अभाज्य संख्याओं का समुच्चय है और (B) (3) के गुणजों का समुच्चय है, तो (\(A\cup B\)') में कितने अवयव हैं?
If \(U={1,2,\ldots,30}\), (A) is the set of prime numbers and (B) is the set of multiples of (3), then how many elements are in (\(A\cup B\)')?
Explanation opens after your attempt
B. (12)
Concept
There are (10) primes in (A), (10) multiples in (B), and \(A\cap B={3}\), so \(|A\cup B|=19\). Hence (|\(A\cup B\)'|=30-19=11); always subtract from (|U|).
Why this answer is correct
The correct answer is B. (12). There are (10) primes in (A), (10) multiples in (B), and \(A\cap B={3}\), so \(|A\cup B|=19\). Hence (|\(A\cup B\)'|=30-19=11); always subtract from (|U|).
Exam Tip
(A) में (10) अभाज्य हैं, (B) में (10) गुणज हैं और \(A\cap B={3}\), इसलिए \(|A\cup B|=19\)। अतः (|\(A\cup B\)'|=30-19=11) नहीं, ध्यान से (30-19=11) है।
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