Getting 10K badges at Khan Academy

Someone pointed me out Khan Academy last summer, and I made an account there, but not until early this year did I come across it again while watching the excellent Crash Course History.

During that time I noticed there was a badge system and when I realised there was all kinds of mathematics materials I got really hooked.

Terminal based math and language exercise programs

My first paid computer job was for the University of Leiden: I had to program software on a PDP-11 system running Unix, that presented children (age 7-14) with mathematics and language exercises.

This was in the time of 300baud modems and character terminals, so a large part of the difficulty lay in the abstraction off the cursor handling (without curses) for the VT-52, Beehive and other terminals that were located in the class rooms of 4 schools (connected to two PDP systems via telefone dial-in lines).

The exercises were simple fill out words missing in a sentence; solve simple equations (5 x 8=..); but also sofisticated “staartdelingen” where multidigit numbers were divided by other multidigit numbers, thereby creating a “staart” (tail) downwards while creating the solution interactively.

Of course we were limited to 25x80 characters and all we had for feedback was the terminal beep, but the kids loved it.

I worked two years on the project under the guidance of Ed van Kan and I learned a lot, both in terms of real programming and in terms of Unix system adminstration.

Khan Academy

The easy excercises at Khan academy, that do not involve graphics look a lot like what I had done. But what interested me more were the advance math skill, as I had been wanting to review them (in case my kids ever ask). After multiple moves (including 8 cross country boundaries) I did not have my old mathematics books and I never got around to visit the second hand bookstore (De Slechte) in Rotterdam to see if they still had them.

The exercises at the Khan Academy are of course slightly different from the dutch explanations I was used to, but the exercises have tips and if that is not enough to refresh my memory they have video instructions associated with them. If you are not refreshing, you probably better start with the videos.

Points and badges

I had already noticed you would get points for finishing watching videos and sometimes badges, but by finishing practise tasks, you really can gather these.

Early April this year I got my “High Five” badge for 5 practise tasks completed. I investigated which other badges were available, how much points you would get for what activities and starting ‘scoring’ without a real goal.

You get points for doing exercises and for completion of rows, the exact amount depending on how many exercises you already did (seems that was not always the case as I have read remarks about people missing answers to keep the points-per-exercise high). Videos seem to give the same amount for watching (once) independent on the length of the video.

Badges come in a large variety, some associated with achieving certain milestones that can be earned only once. Some associated with exercises that can be earned once per exercise subject. A few badges have points associated with them.

Gathering points and badges

Apart from watching videos, the primary means of gathering points is doing exercises. The return on investment for practising the same thing over and over turns down rapidly as the points per correct exercise go down to 5. It does however make sense to (correctly) answer 100 exercises in a row while practising because this gives you 5 badges, and if you do each of the exercises speedy enough you can earn a few badges with points attached to them ( “Picking Up Steam”, “Going Transonic”, “Going Supersonic”, “Sub-light Speed”, “299,792,458 Meters per Second”). All together you can get at 11K points for doing 100 exercises.

Answering the questions requires mastery of the skill, but doing a hundred in a row requires a meditative level of concentration: one error or one answer typed to slow and you have to start from 0.

How fast is fast enough?

Fortunately, looking for what the requirements for the Tesla badge was, I came across an series of articles by Peter Collingridge which pointed out how to get the Tesla badge and that there is an API, which you can explore and that will tell you the maximum time you have for each exercise.

The API really saved me, because some exercises have a ridiculously low (sometimes even 0) time associated with them.

A good calculator (the on screen one is ok, but slower to operate), and being able to type blind (on the numeric keypad), all help to expand the number of exercises that can be done.

You should limit the mixing of exercises from different subjects. I am pretty sure the speed badge counter is reset if you interject an exercise from a different subject. For the “Streak” (Ridiculous, Ludicrous, etc.) this doesn’t seem to be the case, but once I gather the 299,.. badge I normally continue to 100. For trying things out, without interrupting a streak with other exercises you can also create a second account.


For those task that require a lot of time, and have a short response time, I keep notes on the solutions, so that when the same question comes around, I don’t have to recalculate the answer. Sometimes I make screenshots for that purpose. Make sure you organize what you gather, so you can easily access it once you need it. Tthere seem to be a lot of subjects that have random generated values in the exercises, so this doesn’t help for every subject.

There are also two badges that you get when correctly answering after multiple (10 or so) false answers, or answers that required hints. Those don’t bring points, but helped me reach the goal I had set myself: 10000 badges.

10000 Badges

Today I managed to get my 10000 (ten thousand) badge:


Achieving 10000 badges on 2014-06-18

(I did not include the 94 Patches in the count.)

Errors and strange behaviour

I have come across several errors in the answers. You can report these, but you don’t get any feedback if things were solved. What is a problem with that is that these questions come back for master challenges and you don’t know if they are fixed or not, or if they need the faulty answer.

One other thing that is strange is that one of my badges doesn’t show up on the badges page (it does on the total tally on the main user page). When I noticed I made a screenshot of the refreshed badges page, with a pull down of the progress pull down (top right, between “HOME” and your name) and you can see that the latest entry for the earth badge did not register in the acquired badges list. Not sure what is going on there....

What is next?

My next goal could be getting the final missing patches, and then going for 20 million points, maybe the latter gives me another one of the Black Hole badges. If you want to keep an eye on the progress you can visit my profile page.

Gathering points is slowing down though, because the number of subjects for which exercises are available is limited. So I probably will refocus on my work instead of gathering points and badges on Khan Academy in the near future.

Posted on 2014-06-18.