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CA Foundation · Quantitative Aptitude · Permutations and Combinations

How many 4-digit numbers can be formed using the digits 1, 2, 3, 4, 5, 6 where no digit is repeated?

We need to arrange 4 digits from 6 digits without repetition. This is P(6,4) = 6 × 5 × 4 × 3 = 360 four-digit numbers.

  1. A360Correct
  2. B720
  3. C480
  4. D1296

Explanation

This is a permutation problem where we select and arrange 4 digits from 6 available digits without repetition. P(6,4) = 6! / (6-4)! = 6! / 2! = 6 × 5 × 4 × 3 = 360. The distractor 720 results from P(6,3) or miscalculation. The distractor 1296 comes from 6^4, which applies when repetition is allowed.

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