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exactly half of N tickets have the digit 1 on them

Source: Mathematics Regional Olympiad of Mexico Center Zone 2007 P6

November 8, 2021
number theoryDigits

Problem Statement

Certain tickets are numbered as follows: 1,2,3,…,N1, 2, 3, \dots, N . Exactly half of the tickets have the digit 1 1 on them. If NN is a three-digit number, determine all possible values ​​of NN .
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