How many three-digit numbers have all three digits different?
Answer and explanation
Correct answer: C.
- Step 1: The first digit has 9 choices (not 0). Step 2. The second has 9 choices (including 0 but not the first) and the third 8, so . **Answer: . Why not the others:** allows a leading zero, allows repeats, and counts all three-digit numbers.
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