2006 AMC 10A Problem 21
Problem 21 of 25HarderNumber TheoryCounting & Probability
How many four-digit positive integers have at least one digit that is a or a
Answer choices
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Solution
There are four-digit integers. For those avoiding and the leading digit is one of ( choices) and each remaining digit is one of ( choices):
So have at least one or
Thus, the correct answer is E.