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📐 Mathematics  ·  Permutations and Combinations  ·  JEE

How many 4-digit numbers can be formed from 1-9 without repetition?

Answer: 9P4.

  • A 9×8×7×6 = 3024
  • B 9!
  • C 9P4
  • D 9<sup>4</sup>

Correct answer: C. 9P4

Explanation: 9P4 = 9×8×7×6 = 3024. Options A and C are equivalent.

StartABCBCACAB6 ordered outcomes (permutations); pairing AB/BA etc gives 3 combinations

Counting tree for selecting 2 items from {A, B, C} without repetition: 3 x 2 = 6 ordered arrangements.

Concept context

Counting, arrangements, and selections

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