Problem

Source: KAMO 2022 Grade 9 (answer-only question)

Tags: inequalities



Let $a>0$. If the inequality $22<ax<222$ holds for precisely $10$ positive integers $x$, find how many positive integers satisfy the inequality $222<ax<2022$? Note: The first 8 problems of the competition are questions which the contestants are expected to solve quickly and only write the answer of. This problem turned out to be a lot more difficult than anticipated for an answer-only question.