Question
Mathematics Question on permutations and combinations
The letters of the word COCHIN are permuted and all the permutations are arranged in an alphabetical order as in an English dictionary. The number of words that appear before the word COCHIN, is
A
360
B
192
C
96
D
48
Answer
96
Explanation
Solution
Arrange the letters of the word COCHIN as in the order
of dictionary CCHINO.
Consider the words starting from C
.
There are 5! such words. Number of words with the two
C's occupying first and second place = 4!.
Number of words starting with CH, Cl, CN is 4! each
.
Similarly, number of words before the first word
starting with CO = 4! + 4! + 4! + 4! = 96.
The word starting with CO found first in the dictionary
is COCHIN. There are 96 words before COCHIN.