Engineering Board Exam Reviewer · Permutations · medium

How many 4-digit numbers can be formed from the digits 0 to 9 if no digit is repeated?

  1. 5,040
  2. 4,536
  3. 10,000
  4. 4,032

Answer

B. 4,536

Solution

The first digit cannot be 0: 9 choices. Then 9, 8, and 7 choices for the others: 9×9×8×7=4,536.

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