- A81
- B90
- C72
- D100
Step-by-Step Solution
Tens digit 1–9: 9 ways. Units digit: any of the 10 digits except the tens digit, 9 ways. . (90 counts all 2-digit numbers, including 11, 22, …)
Answer: A) 81
How many 2-digit numbers have two different digits?
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