I have finnaly found out how to hack khan academy! this hack gives you a couple of minutes(so the teachers know how long you were on) WITHOUT DOWNLOAD! six steps:
1. All you have to do is a simple lesson.
2. Next do a problem (use a calculator for faster results)
3. Wait a couple of minutes or play a game
4. Go on your "user profile>activity"
5. Refresh the page and you will se that you have two minutes try to do this every 30 secounds (if you want)
6. Have fun hope I helped and sorry I was late!