(6) अलग-अलग चाबियों को (6) अलग-अलग तालों के सामने रखा जाता है। कितने तरीकों में कोई भी चाबी सही ताले के सामने नहीं होगी?
(6) distinct keys are placed against (6) distinct locks. In how many ways will no key be placed against its correct lock?
Explanation opens after your attempt
A. (265)
Concept
This is a derangement of (6) objects, whose number is (!6=265). In exams, when none is in the correct place, think derangement.
Why this answer is correct
The correct answer is A. (265). This is a derangement of (6) objects, whose number is (!6=265). In exams, when none is in the correct place, think derangement.
Exam Tip
यह (6) वस्तुओं का derangement है जिसकी संख्या (!6=265) होती है। परीक्षा में कोई भी सही स्थान पर न हो तो derangement सोचें।
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