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sum 1/a_i <=80

Source: Chile Finals 2012 L2 p2

October 5, 2022
number theorySuminequalities

Problem Statement

Let a1,a2,...,ana_1,a_2,...,a_n be all positive integers with 20122012 digits or less, none of which is a 99. Prove that 1a1+1a2+...+1an80. \frac{1}{a_1}+\frac{1}{a_2}+ ... +\frac{1}{a_{n}}\le 80.