The letters of the word UDAYPUR'' are written in all possible ways with or without meaning and these words are arranged as in a dictionary. The rank of the word UDAYPUR'' is
- A
- B
- C
- D
The letters of the word UDAYPUR'' are written in all possible ways with or without meaning and these words are arranged as in a dictionary. The rank of the word UDAYPUR'' is
Correct answer:C
Standard Method
Given: The word is UDAYPUR.
Find: The dictionary rank of UDAYPUR among all arrangements of its letters.
Arrange the distinct letters alphabetically:
The solution states that we count all words occurring before UDAYPUR in dictionary order by checking, at each position, how many smaller letters can be placed first and then arranging the remaining letters.
Using the stated counting:
Then include the word itself:
Therefore, the correct option is C.
Dictionary Ranking Idea
Given: The letters of UDAYPUR are all distinct.
Find: Its rank in dictionary order.
For dictionary ranking, compare the word from left to right. At each position, count arrangements beginning with letters smaller than the current letter and then sum all such counts. Finally, add to include the given word itself.
From the extracted solution:
Hence,
So the rank of UDAYPUR is .
A common mistake is to stop at the number of words before the given word, , and mark that as the rank. This is wrong because rank counts the position of the word itself as well. Add after counting all preceding words.
Another mistake is to ignore dictionary order and start arranging letters in the order they appear in the word. This is wrong because ranking must be based on alphabetical order. First list the letters as and then compare position by position.
Students may also forget that repeated checking is done at each position, not only for the first letter. This is wrong because dictionary rank depends on all earlier possible prefixes. Count smaller available letters at every step from left to right.
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