Permutations And Combinations Question 294

Question: The number of words which can be made out of the letters of the word MOBILE when consonants always occupy odd places is [RPET 1999]

Options:

A) 20

B) 36

C) 30

D) 720

Show Answer

Answer:

Correct Answer: B

Solution:

  • The word MOBILE has three even places and three odd places. It has 3 consonants and 3 vowels. In three odd places we have to fix up 3 consonants which can be done in $ {}^{3}P_3 $ ways. Now, remaining three places we have to fix up remaining three places we have to fix up remaining three which can be done in $ {}^{3}P_3 $ ways. The total number of ways $ ={}^{3}P_3\times {}^{3}P_3 $ = 36.