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Khan Academy on a Stick

Pre-algebra

Understanding fractions

If you don't understand fractions, you won't be even 1/3 educated. Glasses will seem half empty rather than half full. You'll be lucky to not be duped into some type of shady real-estate scheme or putting far too many eggs in your cake batter. Good thing this tutorial is here. You'll see that fractions allow us to view the world in entirely new ways. You'll see that everything doesn't have to be a whole. You'll be able to slice and dice and then put it all back together (and if you order now, we'll throw in a spatula warmer for no extra charge).

Visualizing equivalent fractions

Do you want 2/3 or 4/6 of this pizza? Doesn't matter because they are both the same fraction. This tutorial will help us explore this idea by really visualizing what equivalent fractions represent.

Equivalent fractions and simplified form

There are literally infinite ways to represent any fraction (or number for that matter). Don't believe us? Let's take 1/3. 2/6, 3/9, 4/12 ... 10001/30003 are all equivalent fractions (and we could keep going)! If you know the basics of what a fraction is, this is a great tutorial for recognizing when fractions are equivalent and then simplifying them as much as possible!

Comparing fractions

In this tutorial, we'll practice understanding what quantities fractions actually represent and comparing those to each other.

  • Decomposing a fraction visually

    It helps to visually understand what decomposing a fraction looks like. We're pretty sure you're going to like this.

  • Decomposing a mixed number

    Decomposing mixed numbers is a pretty straightforward process. It's as simple as adding fractions with like denominators. Watch us do it!

  • Adding up fractions

    We need the sum of all the fractions to equal the given fraction. Can you help us choose which ones to use?

Decomposing fractions

In this tutorial, we'll see that a fraction can be broken up (or decomposed) into a bunch of other fractions. You might see the world in a completely different way after this.

Adding and subtracting fractions with unlike denominators

We've already had some good practice adding fractions with like denominators. We'll now add fractions with unlike denominators. This is a very big deal. After this tutorial, you'll be able to add, pretty much, any two (or three or four or... ) fractions!

Adding and subtracting fractions

You've already got 2 cups of sugar in the cupboard. Your grandmother's recipe for disgustingly-sweet-fudge-cake calls for 3 and 1/3 cups of sugar. How much sugar do you need to borrow from you robot neighbor? Adding and subtracting fractions is key. It might be a good idea to look at the equivalent fractions tutorial before tackling this one.

Adding and subtracting with unlike denominator word problems

You know what a fraction is and are now eager to apply this knowledge to real-world situations (especially ones where the denominators aren't equal)? Well, you're about to see that adding and subtracting fractions is far more powerful (and fun) then you've ever dreamed possible!

  • Multiplying fractions and whole numbers

    Don't let multiplying whole numbers and factions get you down. We got this. This explanation will help you become a pro.

  • Multiplying two fractions: an explanation

    This video will help you think about what it means to multiply two fractions. By drawing the problem and "seeing" the answer, you'll better understand how we arrived at it.

  • Multiplying two fractions: example

    Let's practice multiplying two fractions together. We'll learn to simplify the answer, too.

  • Multiplying negative and positive fractions

    Let's take a stab on practicing one of the most commonly used math skills: multiplying and dividing fractions. We'll use a few examples with negative numbers.

  • Multiplication as scaling

    When multiplying fractions, it's sometimes helpful to view the operation as a kind of scaling--that multiplying the fraction times another creates a fractional proportion, or scale. Watch. You'll understand.

Multiplying fractions

What is 2/3 of 2/3? If 4/7 of the class are boys, how many boys are there? Multiplying fractions is not only super-useful, but super-fun as well.

Multiplying fractions word problems

Multiplying fractions is useful. Period. That's all we really have to say. Believe us don't believe us. You'll learn eventually. This tutorial will have you multiplying in real-world scenarios (which is almost as fun as completely artificial, fake scenarios).

Mixed numbers and improper fractions

We can often have fractions whose numerators are not less than the denominators (like 23/4 or 3/2 or even 6/6). These top-heavy friends are called improper fractions. Since they represent a whole or more (in absolute terms), they can also be expressed as a combination of a whole number and a "proper fraction" (one where the numerator is less than the denominator) which is called a "mixed number." They are both awesome ways of representing a number and getting acquainted with both (as this tutorial does) is super useful in life!

Mixed number addition and subtraction

You know the basics of what mixed numbers are. You're now ready to add and subtract them. This tutorial gives you plenty of examples and practice in this core skill!

Mixed number multiplication and division

My recipe calls for a cup and a half of blueberries and serves 10 people. But I have 23 people coming over. How many cups of blueberries do I need? You know that mixed numbers and improper fractions are two sides of the same coin (and you can convert between the two). In this tutorial we'll learn to multiply and divide mixed numbers (mainly by converting them into improper fractions first).

Decimals and fractions

If you already know a bit about both decimals and fractions, this tutorial will help build a bridge between the two. Through a bunch of examples and practice, you'll be able operate in both worlds. Have fun!

Dividing fractions

This is one exciting tutorial. In it, we will understand that fractions can represent division (and the other way around). Then we will create fractions by dividing whole numbers and then start dividing the fractions themselves. We'll see that dividing by something is the exact same thing as multiplying by that thing's reciprocal!

Dividing fractions by fractions

In this tutorial, we'll become fraction dividing experts! In particular, we'll understand what it means to divide a fraction by another fraction. Too much fun!!!

Number sets

The world of numbers can be split up into multiple "sets", many of which overlap with each other (integers, rational numbers, irrational numbers, etc.). This tutorial works through examples that expose you to the terminology of the various sets and how you can differentiate them.