Khan Academy | High tech and art in the school. |
With a library of over 3,000 videos covering everything from arithmetic to physics, finance, and history and hundreds of skills to practice, we're on a mission to help you learn what you want, when you want, at your own pace.

Videos de 9-10 minutos de longitud en los que se explica en cada video, con sencillez y claridad, un concepto matemático o una forma de resolver problemas. ¡Todos hechos por la misma persona!, Sal Kahn.

Via José Antonio Alonso Sancho