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NDA 2026
Exam
NDA
Year
2026
Subject
Mathematics
Chapter
Permutation and Combination

NDA 2026 · Mathematics · Permutation and Combination

Passage: A 4-digit number is selected at random formed by using the...

Passage: A 4-digit number is selected at random formed by using the digits 00, 11, 22, 33 and 44 (where repetition of digits is not allowed).

Question: What is the probability that the number selected is divisible by 22 ?

Options

  1. A58\dfrac{5}{8}
  2. B38\dfrac{3}{8}
  3. C18\dfrac{1}{8}
  4. D524\dfrac{5}{24}

Correct answer

A. 58\dfrac{5}{8}

Step-by-step solution

Total number of 4-digit numbers formed using 0,1,2,3,40, 1, 2, 3, 4 without repetition:
The thousands place can be filled in 44 ways (excluding 00).
The remaining 33 places can be filled in 4P3=24^{4}P_{3} = 24 ways.
Total numbers =4×24=96= 4 \times 24 = 96.

For the number to be divisible by 22, the units digit must be 0,20, 2, or 44.

Case 1: Units digit is 00.
The remaining 33 places can be filled in 4P3=24^{4}P_{3} = 24 ways.

Case 2: Units digit is 22 or 44.
The units place can be filled in 22 ways.
The thousands place can be filled in 33 ways (excluding 00 and the units digit).
The remaining 22 places can be filled in 3P2=6^{3}P_{2} = 6 ways.
Number of such numbers =2×3×6=36= 2 \times 3 \times 6 = 36.

Total number of even 4-digit numbers =24+36=60= 24 + 36 = 60.

Required probability =6096=58= \dfrac{60}{96} = \dfrac{5}{8}.

Answer: 58\dfrac{5}{8}
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