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📐 Mathematics  ·  Permutations and Combinations  ·  JEE

ABCD... if A must be first: arrangements of 5 people ABCDE with A first:

Answer: 4!.

  • A 4!
  • B 5!
  • C 3!
  • D 120

Correct answer: A. 4!

Explanation: A fixed in position 1. Remaining 4 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

Read the full Permutations and Combinations notes →