यदि \(A=\{1,2,3\}\), तो (\mathcal{P}(A)) में कितने तत्व ऐसे हैं जिनमें (1) अवश्य है?
If \(A=\{1,2,3\}\), how many elements of (\mathcal{P}(A)) must contain (1)?
Explanation opens after your attempt
Correct Answer
A. (4)
Concept
Fix (1), then each of the remaining (2) elements may be chosen or not, giving \(2^2=4\) subsets. For a fixed element, take powers over the remaining elements.
Why this answer is correct
The correct answer is A. (4). Fix (1), then each of the remaining (2) elements may be chosen or not, giving \(2^2=4\) subsets. For a fixed element, take powers over the remaining elements.
Exam Tip
(1) को निश्चित रखकर बाकी (2) तत्वों को चुनने या न चुनने के \(2^2=4\) तरीके हैं। निश्चित तत्व वाले प्रश्न में बाकी तत्वों पर घात लगाएं।
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