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imc

number theory intermediate

Problem

How many of the base-ten numerals for the positive integers less than or equal to contain the digit ?
(A)
(B)
(C)
(D)
Solution
We can use complementary counting. There are positive integers in total to consider, and there are one-digit integers, two digit integers without a zero, three digit integers without a zero, and four-digit integers starting with a 1 without a zero. Therefore, the answer is .
Final answer
A