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CA Foundation · Quantitative Aptitude · Permutations and Combinations

Which of the following statements about factorial notation is correct?

The correct statement is that 0! = 1 and 1! = 1. By convention 0! equals 1, so formulas like nCn work. Adding inside the bracket does not split: 5! is 120 while 3! + 2! is only 8.

  1. A0! = 0
  2. B5! = 5 × 4 × 3 × 2
  3. C0! = 1 and 1! = 1Correct
  4. D(3 + 2)! = 3! + 2!

Explanation

By definition 0! = 1 and 1! = 1. 0! is not 0, 5! = 120 includes the factor 1 (and equals 5×4×3×2×1, which is the same value as 5×4×3×2 but is not the full definition used; the option given is incomplete as a stated rule), and (3+2)! = 120 while 3!+2! = 8, so the last is false.

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