The correct answer to the question was 25. Whether the student solved it or not, their act of thinking about it for a few minutes will have prepared them to learn more deeply.
The next stage is a video explanation of the problem by Po-Shen Loh, who teaches all of the lessons. The problems are carefully chosen to have multiple solutions, some of which teach advanced concepts using simple language. Each explanation video is a deep math lesson that not only shares methods useful for exams, but also teaches how to understand math.
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