MCQMediumJEE 2026Applications of P&C

JEE Mathematics 2026 Question with Solution

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

    15781578

  • B

    15791579

  • C

    15801580

  • D

    15811581

Answer

Correct answer:C

Step-by-step solution

Standard Method

Given: The word is UDAYPUR.

Find: The dictionary rank of UDAYPUR among all arrangements of its letters.

Arrange the distinct letters alphabetically:

A,D,P,R,U,YA, D, P, R, U, Y

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:

Number of words before UDAYPUR=1579\text{Number of words before UDAYPUR} = 1579

Then include the word itself:

Rank=1579+1=1580\text{Rank} = 1579 + 1 = 1580

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 11 to include the given word itself.

From the extracted solution:

  1. Arrange letters alphabetically.
  2. Count permutations starting with smaller letters at each position.
  3. Total preceding permutations are 15791579.
  4. Add 11 for the word itself.

Hence,

Rank=1579+1=1580\text{Rank} = 1579 + 1 = 1580

So the rank of UDAYPUR is 15801580.

Common mistakes

  • A common mistake is to stop at the number of words before the given word, 15791579, and mark that as the rank. This is wrong because rank counts the position of the word itself as well. Add 11 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 A,D,P,R,U,YA, D, P, R, U, Y 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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