Alphabetical arrangement of letters: A,D,I,N
⇒ 1st word: ADIIN
To find other words:
Case 1: words starting with A
Number of words = \(\frac{4!}{2!}\) = 12
⇒ 13th word starts with D and is DAIIN
Case 2: words starting with D
Number of words = \(\frac{4!}{2!}\) = 12
Case 3: Words starting with I
Number of words = 4! = 24
⇒ (12+12+24+1)th = 49th word starts with N and is NAIID
Case 4: Words starting with N
Number of words = \(\frac{4!}{2!}\) = 12
⇒ (48+12)th word is the last word which starts with N
⇒ 60th word = NDIIA
1st word: ADIIN
13th word: DAIIN
9th word: NAIID
60th word: NDIIA