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. The videos themselves are split into short segments with mini-questions at the end.
Click on the video to start!
When you've finished watching the video and are ready to answer the mini-question, choose your answer below: