Permutations And Combinations Question 178

Question: The number of ways of choosing a committee of two women and three men from women and six men. If Mr. A refuses to serve on the committee if Mr. B is a member and Mr. B can only serve, if Miss C is the member of the committee is

Options:

A) 60

B) 84

C) 124

D) none of these

Show Answer

Answer:

Correct Answer: C

Solution:

  • [c] (i) Miss C is taken [a] B included
    $ \Rightarrow $ A excluded $ {{\Rightarrow }^{4}}C_1{{\times }^{4}}C_2=24 $ [b] B excluded $ {{\Rightarrow }^{4}}C_1{{\times }^{5}}C_3=40 $ Miss C is not taken

$ \Rightarrow $ B does not come $ {{\Rightarrow }^{4}}C_2{{\times }^{5}}C_3=60 $

$ \Rightarrow $ Total=124 Alternate method: Case I: Mr. B is present

$ \Rightarrow $ A is excluded and C included Hence, the number of ways is $ ^{4}C_2^{4}C_1=24 $ . Case II: Mr. ‘B’ is absent

$ \Rightarrow $ No constraint Hence, the number of ways is $ ^{5}C_3^{5}C_2 $ =100.

$ \therefore $ Total = 124.