Question: The number of permutations of the letters of the word HINDUSTAN such that neither the pattern ?HIN? nor ?DUS? nor ?TAN? appears, are
Options:
A) 166674
B) 169194
C) 166680
D) 181434
Show Answer
Answer:
Correct Answer: B
Solution:
- [b] Total number of permutations $ =\frac{9!}{2!} $
Number of those containing $ ‘HIN’ $ $ =7! $
Number of those containing ?DUS? $ =\frac{7!}{2!} $
Number of those containing ?TAN? $ =7! $
Number of those containing ?HIN? and ?DUS? $ =5! $
Number of those containing ?HIN? and ?TAN? $ =5! $
Number of those containing ?TAN? and ?DUS? $ =5! $
Number of those containing ?HIN? and ?DUS? and ?TAN?=3!
Required number
$ =\frac{9!}{2!}-( 7!+7!+\frac{7!}{2} )+3\times 5!-3!=169194. $