How many even four-digit numbers can be formed from the digits if no digit may be used twice?
Answer and explanation
Correct answer: D.
- Step 1: The last digit must be or : choices. Step 2. The first three places are filled from the remaining digits: ways. Step 3. Total: . **Answer: . Why not the others:** : This counts only one choice of last digit. : counts arrangements of only three of the digits, . : This doubles the correct count.
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