यदि (n(A)=78), (n(B)=69), (n(C)=63), (n\(A\cap B\)=30), (n\(B\cap C\)=25), (n\(C\cap A\)=21) और (n\(A\cap B\cap C\)=9) है, तो केवल (A) में कितने तत्व हैं?
If (n(A)=78), (n(B)=69), (n(C)=63), (n\(A\cap B\)=30), (n\(B\cap C\)=25), (n\(C\cap A\)=21) and (n\(A\cap B\cap C\)=9), then how many elements are only in (A)?
Explanation opens after your attempt
A. (36)
Concept
Only (A=78-30-21+9=36). In three sets, the centre is subtracted twice, so add it back.
Why this answer is correct
The correct answer is A. (36). Only (A=78-30-21+9=36). In three sets, the centre is subtracted twice, so add it back.
Exam Tip
केवल (A=78-30-21+9=36) है। तीन समुच्चयों में केंद्र दो बार घटता है इसलिए उसे वापस जोड़ें।
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