Question
Mathematics Question on Permutations
The letters of the word MODESTY are written in all possible orders and these words are written out as in a dictionary then the rank of the word MODESTY is
5040
720
1681
2520
1681
Solution
The words in a dictionary are arranged in an alphabetical manner.
Words starting with D are 6! = 720, start with E are 720. start with MD are 5! = 120 and start with ME are 120. Now the first word that starts with MO is nothing but MODESTY. Hence rank of MODESTY is 1681.
Alternate Approach-1
The number of words starting with D, arranging the other 6 letters = 6! =720
The number of words starting with E = 6! = 720
The number of words starting with M = 6! = 720 but one of these words is MODESTY
The number of words starting with MD = 5! =120
The number of words starting with ME = 5! =120
Now the first-word start with MO is MODESTY.
Hence, the rank of MODESTY = 720 + 720 + 120 + 120 + 1 =1681
Read More: Permutations and Combinations