How many distinct 4-digit PIN codes can be formed using the digits 0 to 9 if no digit may be repeated?
Answer and explanation
Correct answer: A.
- Step 1: The problem asks for the number of permutations of 10 digits taken 4 at a time: . Step 2. Compute: . **Answer: . Why not the others:** allows digit repetition; 210 computes combinations where order is ignored.
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