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A four-digit number is selected at random. What is the
Chapter , Problem 23(choose chapter or problem)
A four-digit number is selected at random. What is the probability that its ones place is less than its tens place, its tens place is less than its hundreds place, and its hundreds place is less than its thousands place? Note that the first digit of an n-digit number is nonzero.
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QUESTION:
A four-digit number is selected at random. What is the probability that its ones place is less than its tens place, its tens place is less than its hundreds place, and its hundreds place is less than its thousands place? Note that the first digit of an n-digit number is nonzero.
ANSWER:Step 1 of 2
A four-digit number is selected at random.
A four-digit number can be started with any digit between 1 to 9. So, the thousand position can be filled in 9 different ways. For each of these 9 ways, the remaining three places can be filled in ways.
Therefore, there are total four-digit numbers.