[ericxtang]

Classroom setting is really not the best setting for studying math. Studying new materials in math needs complete concentration, a 2-3 minutes mind-wondering can cost your the entire period, since new concepts/abstractions in math build on top of each other.

It's very difficult to concentrate for a 40 min period, especially considering students just came from other classes that could be just as mentally challenging.

I think Khan academy does a good job at this. A 15-minute long video is a much more consumable chunk of knowledge.