Khan Academy, which took the world by storm with its simple, free educational materials a couple years ago, announced a big milestone this week. They’ve surpassed 3 billion problems answered.

That means three billion people have answered quiz questions after watching video materials, and learning things. For free.

The Academy said in a blog post:

We asked Sal what he thought of this, and he said, “Personally, I don’t know what all the fuss is about. I’m waiting for us to hit 3 141 592 653 problems solved before I get really excited.” Can you help us get to pi billion?!

The rate at which everyone is learning on Khan Academy is astounding: it took less than a year to grow from 2 billion to 3 billion problems answered! Way to go!

They might get to that next billion sooner rather than later. Earlier this month, the Academy released an app for the Xbox One. VentureBeat shared this:

“We’re always looking for innovative, new experiences to share with our fans on Xbox. The addition of Khan Academy on Xbox One is an important milestone in our commitment to delivering rich and differentiated apps on the platform,” said Chris Meador, Xbox’s director of product marketing. ” The Khan Academy app covers a ton of useful topics and includes thousands of educational videos, plus the Xbox One interface makes it easy to use on your TV.”

Khan Academy Sal Khan recently spoke at the Atlantic’s Navigate Tech Conference. The publication has a good recap of what he had to say here.

Image via Khan Academy