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2009/10 AHSMC Part 1 Problem 6

Problem 6 of 16

Among the positive integers with six digits in their base-1010 representation, the number of those whose digits are strictly increasing from left to right is

Answer choices

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Solution

We can choose any six of the nine non-zero digits. The number of choices is (96)=84\binom{9}{6} = 84. Each choice gives rise to a unique number. The answer is (B).

University of Alberta