A 33-year-old ex-hedge fund analyst, Salman Khan, is making a second career out of tutoring kids around the world on math, finance and science with 1400 short online videos. The videos, which are also posted on YouTube, are on simple mathematical functions as well as algebra, physics, geometry, trigonometry, calculus, finance, statistics, probability, economics, physics.

Currently, 100,000 students view his free Khan Academy videos every month (there are 40,000 video views per month). While the Academy's content is mainly concerned with pre-college mathematics and physics, Khan says his long-term goal is to provide tens of thousands of videos on all sorts of subjects including history and grammar and to create a free ,world-class virtual school.

In the brief videos (most are under 10 minutes long), Khan doesn't appear on camera but uses an electronic chalkboard program (Microsoft Paint) to illustrate his lessons with brightly colored "chalk." Students only hear his voice and Khan has compared the effect to sitting next to someone and working out a problem.

Khan said he got the idea for his online lessons when he was helping a young cousin to improve in math and started posting her math lessons on YouTube. Offline versions of the videos have been distributed by not-for-profit groups to rural areas in Asia, Latin America, and Africa.

In a report aired on PBS earlier this year, one student remarked, "Teachers can't go at a pace that's perfect for everyone. I like the concept of knowing something in class but going back and pressing pause or rewind and actually getting a deeper understanding of it."

A teacher commented that Khan's online videos are not a substitute for the conversations teachers and students have in the classroom, but that they may be especially valuable for shy students who don't ask questions.

Khan said he kept the lessons short because of YouTube restrictions on length of videos, but it turns out that short is better because research shows 10 minutes is as long as many people can maintain high levels of concentration. The Khan Academy and Salman Kahn won the 2009 Tech Award in Education.

To see the list of lesson videos, go to the Khan Academy site: http://www.khanacademy.org