2023 OIM Problems/Problem 1
Problem
Let 
be a positive integer. The following 35 multiplications are performed:
![\[1 \cdot n,2 \cdot n,\cdots ,35 \cdot n\]](http://latex.artofproblemsolving.com/9/4/7/9477f0b5c68ea26e533cb90536eb88aeec7c2de4.png)
Show that in at least one of these results the digit 7 appears at least once.
Solution
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See also
https://sites.google.com/associacaodaobm.org/oim-brasil-2023/pruebas
