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Question

Mathematics Question on permutations and combinations

If all permutations of the letters of the word are arranged in the order as in a dictionary, what is the 49th49^{th} word?

A

AAGIN

B

NAAGI

C

IAAGN

D

GAAIN

Answer

NAAGI

Explanation

Solution

Starting with letter AA, and arranging the other four letters, there are 4!=244! = 24 words. These are the first 2424 words. Then starting with GG, and arranging A,A,IA, A, I and NN in different ways, there are 4!2!1!1!=12\frac{4!}{2!1!1!} = 12 words. Next the 37th37^{th} word starts with II. There are again 1212 words starting with II. This accounts up to the 48th48^{th} word. The 49th49^{th} word is NAAGINAAGI.