How many distinct 4-digit numbers can be formed using the digits 1, 2, 3, 4, 5, and 6 if no digit may be repeated?
Answer and explanation
Correct answer: D. 360
- Step 1: Permutation formula P(n, k) = n! / (n - k)!.
- Step 2: Here n = 6 available digits and k = 4 digits to choose in order.
- Step 3: P(6, 4) = 6 5 4 * 3 = 360.
Answer
360.
Why not the others: 120 is 5 4 3 * 2; 720 is 6! (all 6 digits); 240 is an arithmetic error.
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