एक (5)-अंकीय कोड (1,2,3,4) से बनता है। हर अंक कम से कम एक बार आना चाहिए। ऐसे कोड कितने हैं?
A (5)-digit code is formed using (1,2,3,4). Each digit must appear at least once. How many such codes are possible?
Explanation opens after your attempt
C. (240)
Concept
One digit appears twice and the others appear once each. The repeated digit has (4) choices and arrangements are (5!/2!), giving (240).
Why this answer is correct
The correct answer is C. (240). One digit appears twice and the others appear once each. The repeated digit has (4) choices and arrangements are (5!/2!), giving (240).
Exam Tip
एक अंक दो बार आएगा और बाकी एक-एक बार आएंगे। दोहरने वाला अंक (4) तरीकों से और व्यवस्थाएं (5!/2!) तरीकों से हैं, कुल (240) है।
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