Statistics And Probability Question 207

Question: The letter of the word `ASSASSIN’ are written down at random in a row. The probability that no two S occur together is

[BIT Ranchi 1990; IIT 1983]

Options:

A) $ \frac{1}{35} $

B) $ \frac{1}{14} $

C) $ \frac{1}{15} $

D) None of these

Show Answer

Answer:

Correct Answer: B

Solution:

  •                 Total ways of arrangements  $ =\frac{8\,!}{2\,!.4\,!} $                      $ \bullet \,w\bullet x\bullet y\bullet z\bullet  $                     Now ?S? can have places at dot?s and in places of  $ w,x,y,z $  we have to put  $ 2\,A's, $  one  $ I $  and one  $ N. $                     Therefore favourable ways  $ =5( \frac{4\,!}{2\,!} ) $                     Hence required probability  $ =\frac{5\,.\,4\,!2\,!4\,!}{2\,!8\,!}=\frac{1}{14}. $