Problem 7, Combinatorics

I proposed this problem in the last mathematical competition hosted on the Italian ‘gasmatematica’ website. The numbers from 000 to 999 must be put into some boxes, numbered from 00 to 99. If the label of a box is equal to a number with one digit removed, then the number can be put in that […]

Hidden Telescoping Sum

Here’s an exercise I proposed in an online competition. You have the following sequence: Find the integer part of: Now, notice that Hence By substitution, we have that the sum telescopes and reduces to Since is a very large number (the sequence has a quadratic increasing rate), we have that the integer part of the […]

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