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📐 Mathematics  ·  Permutations and Combinations  ·  JEE

The number of ways to arrange 4 books on a shelf:

Answer: 24.

  • A 4
  • B 12
  • C 24
  • D 16

Correct answer: C. 24

Explanation: 4P4 = 4! = 24. All 4 books can be arranged in 4! = 24 ways.

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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