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Dutch Mathematical Olympiad

Netherlands number theory

Problem

For the second round of the Mathematical Olympiad, 999 students are invited. Melanie creates invitation letters in order of participant number: . For some values of , she notices the following: the number of participant numbers from up to and including ending in a is exactly equal to the integer formed by the last two digits of . For how many values of (with ) does this hold?
Solution
9
Final answer
9

Techniques

Modular ArithmeticIntegers