The Khan Academy offers free educational videos on their site that stay true to that spirit. The team’s mission is to “deliver a world-class education to anyone anywhere”. For now, that’s more than 2100 educational videos with a strong emphasize on Math and Science. All lessons have been created by a single teacher, Mr. Kahn himself.

The videos on site are currently offered in English. The academy is looking for translators and teachers to offer videos in other languages.

All videos that I watched so far are easy to understand, even for users with little or even no experience on the subject. It is on the other hand important to follow the playlist on site, as the lessons may build up on each other. So, instead of starting with complex numbers you should probably start with simple equations or even at the very beginning, at basic addition and subtraction.

Most lessons have a playtime of around ten minutes. They are available for download right on the Khan Academy website. Next to the download are exercises which are only available for logged in users. Creating a user account is free on the other hand, and it is possible to link an existing Google or Facebook account with the service.

Exercises are individually selectable after log in, or directly on the video pages.

Basic exercises display a form on the page where the answer needs to be entered; More advanced challenges may display multiple choice answers and additional tools like a scratch pad. The site keeps track of your progress. Hints are available to help you solve a challenge.

One interesting feature are the badges that users can earn. They are very similar to game achievements and used for motivational purposes. Users can earn badges for correctly answering a set amount of problems in a row, completing a specific amount of exercises or archiving proficiency in a specific field.

Registered users can track their exercise and video watching progress on site, which is another benefit of becoming a member.

Teachers can make use of the videos and exercises on the Khan Academy as well. They can create classes which students can join. They then have the opportunity to watch their classes progress and achievements.

Here are some of the topics covered on the Khan Academy.

• Pre-algebra, Lessons that prepare for the Algebra courses. Teaches exponents, logarithm properties, scientific notation, fractions
• Algebra – Basic algebra to algebra II, includes equations, functions, complex numbers, conic sections and 180 worked examples.
• ck12.org Algebra 1 Examples
• Probability – Best watched after basic algebra
• Precalculus – Should be watched after finishing the Algebra playlist.
• Arithmetic – the most basic math playlist. Includes addition, subtraction, multiplication, division, decimals, percent.
• Banking and Money – Teaches how banks work and money is created. Additional but separate groups include Credit Crisis, Currency, Current Economics and Finance.
• Biology – Includes lessons on evolution, species, cells, cancer, viruses, bacteria, photosynthesis and cells.
• Calculus – Offers lessons on limits, integrals, integrals, Green’s theorem, gradients or polynomial approximation of functions.
• California Standards test Algebra and Geometry
• Chemistry – Atom theory, periodic table, kinetics, acid titration, pH, carbon 14 dating
• Organic Chemistry – Naming examples, Amine, Nucleophilicity, E1 and E2 Reactions
• Cosmology and Astronomy – Earth, Sun, Univers, Parsec definition, big bang introduction, plate tectonics
• Developmental Math – Whole Numbers, Laws, Mixed Numbers, Order of operations, exponents, fractions, integers, polynomials, units
• Differential Equations – Includes exact equations, integrating factors, undetermined coefficients, Laplace Transform, Theorems
• Geometry – Angles, Pythagorean Theorem, Triangles, Cylinder Volume, Heron’s Formula
• Trigonometry – Should be watched after Geometry lessons. Trigonometric functions, problems, polar coordinates
• History – US, French, Vietnam
• Linear Algebra – Matrices, vectors, vector spaces, transformations
• Physics – Includes lessons on motion, Newton’s Laws, Magnetism, Circuits, Fluids.
• Statistics – Will eventually cover all major topics of a first-year statistics course.

Some of the topics mentioned in this little overview may intimidate you. That should not be the case as everything builds up on each other. Plus, the explanation and teaching is really easy to understand and follow, and you can post questions on each video page that other users can answer to help you understand the concepts.

The videos can also be used to teach children those lessons, in addition to the lessons they have at school. This can be supplementary or in advance. It is best if an adult watches the videos with them, especially for the very young ones to be there in case additional explanations or help is needed.

You can watch all educational videos on the Khan Academy website. This site is highly recommended to everyone who wants to learn or refresh math or science. Could also be interesting for parents to keep up with their children’s school progress.

The left side displays examples while the right side displays the solution for that example. This means that Algebasics is useful for those who need more practice in solving certain equations or grasping concepts. What I like is that you get a visual presentation of the example plus a voice that is explaining the steps.

It’s much like school without a visible teacher and classmates. What I do not like that much is that there is practically no explanation of the underlying concepts. A introductory section for every section would have been nice.

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Algebasics

Lower difficulty levels remove the more complex operations such as multiplications and divisions from the pool of possible math questions making it an ideal program for children of all ages. (almost). The first difficulty levels ask less questions and easier questions. Level 1 for instance is only about addition of small numbers between 0-9.

Players get rewarded with points and ninja ranks to motivate them further. I think Math Ninja is a great way to improve the math skill of your children over time in a playful environment.

Update: The author’s website is no longer available. We have uploaded the latest version of Math Ninja to our servers. Please click on the following link to download the program: Math Ninja (2)

The latest version of the program supports both negative and positive numbers. You have got only ten seconds to write down the result of the equation. There is unfortunately no option to change the time limit. Especially younger children may have problems because of this.

The program displays some basic ninja animations on the screen which add to the fun of the program.