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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

A

5040

B

720

C

1681

D

2520

Answer

1681

Explanation

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