I discovered Salman Khan quite by accident. I wanted to calculate the percentage of a certain number and realized that I have forgotten how to. So I did a google to refresh my memory, and that’s when I came across the Khan Academy.

Virtual school: Salman Khan’s teaching methodology is detailed

The 33-year-old Khan runs a one-of-a-kind website called the Khan Academy (www.khanacademy.org) where he has around 2,000 video tutorials for high-school students on subjects ranging from mathematics, chemistry and physics to history and astronomy—and yes, how to calculate percentages. Bill Gates has been quoted as calling it “unbelievable" and saying he’s been using it with his children. In September, Google gave Khan $2 million (around Rs9 crore) “to support the creation of more courses" and “to translate their core library into the world’s most widely spoken languages".

Khan is a quintessential teacher: He is meticulous and articulate, explains every step to the smallest detail, doesn’t talk down and has a nice and easy way. I’ve watched some of his tutorials—how is gender determined in an organism, the scale of the solar system and an introduction to exchange-rate fluctuations—and each one of them stands out for clarity. You never see Khan in the 15-minute video (that’s the approximate duration of each tutorial); you hear his voice and see a blackboard and a cursor doodling on it.

The story behind Khan’s virtual school goes back some seven years when his aunt asked him to teach mathematics to her daughter in high school. The only problem was that Khan and the young girl lived in different cities. So he decided to remotely tutor her: They would talk on the phone and use a popular doodling program as a notepad to discuss equations. Soon other members of the family and friends sought his help for their children. So he started to post YouTube videos, which anyone could watch in their own time.

Three years ago Khan gave up his million-dollar job to start the Khan Academy, the “world’s first free, world-class virtual school where anyone can learn anything". His YouTube videos (they now include IIT Joint Entrance Exam lessons) have been viewed over 40 million times.

You can look up how to do fractions in math and help your children with their homework without having to send them for tuitions. Or you can also use it to learn a new subject. The best thing is that it’s all there on the Net. For students in high school or even college, for those who want to crack SATs (the Scholastic Aptitude Test and Scholastic Assessment Test), for IIT aspirants and for people like me who have forgotten what they learnt in college, it’s an outstanding resource. What’s more, you don’t have to pay to learn. It’s free.

Many colleges abroad have put some of their lectures online but the Khan Academy is a one-man endeavour, and a virtual classroom at its best. You can go to his school for an amazing range of subjects—from basic addition (1+1=2) to age word problems (“In four years Ali will be three times as old as he is today. How old is Ali today?"), and even a few interesting brain-teasers such as the one in which aliens have abducted 10 humans.

The aliens tell the humans that in 24 hours they will be put through a test: They will be made to stand in a line in a dark room and a hat will be placed on each of their heads. The hats will either be purple or green. They could be all purple, all green, or some of either colour. Each human will be able to see the colour of the other nine hats but not his or her own. The aliens will start with the person at the back of the line and ask: “What colour is the hat on your head?" You get it wrong and you die along with the tenth of the human race you represent. You have 24 hours to think. Remember, there is only one answer: purple or green. And, says Khan, there is a solution that guarantees that nine of you will live. Visit the Khan Academy website to find out how.

Shekhar Bhatia is a former editor, Hindustan Times, a science buff and a geek at heart.

Write to him at thesmartlife@livemint.com