I'm here today to talk about the two ideas that,

at least based on my observations at Khan Academy,

are kind of the core, or the key leverage points for learning.

And it's the idea of mastery

and the

Read more

Transcriber:

This is a lump of coal.

It was mined a while ago in the Ruhr region in Germany,

about 50 miles from where I grew up.

As coal goes, it's actually quite high-end.

It's very dry, it has a h

Read more