MathematicsLinear PermutationsJEE Advanced 2008Moderate
Visualized Solution (English)
Word Analysis
- Word: ENDEANOEL
- Total letters: 9
- Letter counts: E:3,N:2,D:1,A:1,O:1,L:1
Part (A): Word ENDEA as a Block
- Treat ENDEA as a single block.
- Remaining letters: N,O,E,L
- Total units to arrange: 1 (block)+4 (letters)=5
- Number of ways = 5!
- Matching: (A)→(p)
Part (B): Fixed E at Ends
- Fixed positions: E_______E
- Remaining letters: N,D,E,A,N,O,L (Total 7)
- Repetitions: N occurs 2 times.
- Arrangements = 2!7!=27×6×5!=21×5!
- Matching: (B)→(s)
Part (C): Restrictions on Last 5 Slots
- Constraint: D,L,N,N cannot be in positions 5,6,7,8,9.
- Therefore, D,L,N,N must occupy positions 1,2,3,4.
- Arrangement of first 4: 2!4!=12
- Remaining letters (E,E,E,A,O) in last 5: 3!5!=20
- Total = 12×20=240=2×5!
- Matching: (C)→(q)
Part (D): A, E, O at Odd Positions
- Odd positions: 1,3,5,7,9 (5 slots)
- Letters for odd slots: A,E,E,E,O (Total 5)
- Arrangement (Odd): 3!5!=20
- Letters for even slots (2,4,6,8): N,N,D,L
- Arrangement (Even): 2!4!=12
- Total = 20×12=240=2×5!
- Matching: (D)→(q)
Final Conclusion
- Final Matchings:
- (A)→(p)
- (B)→(s)
- (C)→(q)
- (D)→(q)
- Key Takeaway: Handle restricted positions or blocks first before arranging the rest.
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