Multiplication and division : Khan Academy on a Stick

Khan Academy on a Stick

Arithmetic

Concept of multiplication and division

Let's introduce ourselves to two of the most fundamental ideas in all of mathematics: multiplication and division!

Number line 1
Basic multiplication
Introduction to multiplication
Multiplication 2: The multiplication tables
Introduction to the multiplication tables from 2-9.
Example: Ways to represent multiplication
Multiplying Whole Numbers and Applications 1
Multiplication 3: 10,11,12 times tables
Multiplication 3: Learning to multiply 10, 11, and 12.

Basic multiplication

If 3 kids each have two robot possums, how many total robot possums do we have? You liked addition, but now you're ready to go to the next level. Depending on how you view it, multiplication is about repeated addition or scaling a number or seeing what number you get when you have another number multiple times. If that last sentence made little sense, you might enjoy this tutorial.

Division 1
Introduction to division
Example: Expressing division in multiple ways
Dividing Whole Numbers and Applications 1

One-digit division

Every time you split your avocado harvest with your 10 pet robot possums, you've been dividing. You don't farm avocados? You only have 8 robot possums? No worries. I'm sure you've divided as well. Multiplication is awesome, but you're ready for the next step. Division is the art of trying to split things into equal groups. Like subtraction undoes addition, division also undoes multiplication. After this tutorial, you'll have a basic understanding of all of the core operations in arithmetic!

Comparing with multiplication: basic exercises
If you think about it, multiplying is just another way of comparing numbers. How do we compare 4 and 20 using multiplication? Let's find out together.
Comparing with multiplication: age
Multiplication helps us compare ages. Hint: learn those multiplication tables. They really help on problems like these.
Multiplication word problem example 1
Division word problem example 1
Comparing with multiplication: Ron and Hermione strength
You read that right! We're comparing the strength of Ron and Hermione using multiplication. Who said math has to be boring?

Starter multiplication and division word problems

Math is super useful in the real world. In this tutorial, we'll get some practice figuring out things that would have been tough without the powerful tools of multiplication and division!

Multiplying by multiples of 10
Multiplying: 2 digits times 1 digit
Let's start by solving a basic multiplication problem. No carrying of numbers in this example!
Multiplying: 3 digits times 1 digit
How about this example? We're going to multiply a 3 digit number by a 1 digit number. Again, no carrying involved.
Multiplying: 2 digits times 1 digit (with carrying)
We use something called the standard method which involves writing the larger of the two numbers on top. Watch.
Multiplying: 3 digits times 1 digit (with carrying)
We're carrying numbers in this example. Everyone needs a hand now and then, right?
Multiplying: 4 digits times 1 digit (with carrying)
This is getting fun! We're now multiplying FOUR digits times one digit. Remember to carry!
2-digit times a 2-digit number
Multiplying a 2-digit number times a 2-digit number
Example: 2-digit times 2-digit
Multiplying Whole Numbers and Applications 2
Multiplying multiple digit numbers
Working our way up to multiplying multiple-digit numbers with each other. We'll go slow so you can follow along.
Multiplication estimation example
Estimating the product of two, 2-digit numbers
Multiplication 7: Old video giving more examples
2 examples of multiplying a 3 digit number times a 2 digit number. 1 example of multiplying a 3 digit number times a 3 digit number.

Multi-digit multiplication

You know your multiplication tables and are ready to learn how to multiply *any* number (actually, any whole number). Imagine the possibilities! This tutorial will make you unstoppable.

Introduction to long division
Dividing into larger numbers. Introduction to long division without remainders
Dividing numbers: intro to remainders
Do you like leftovers? (personally, we think they are delicious!). Those leftovers are like remainders in divisions problems. They're not bad. They just...are.
Dividing numbers: example with remainders
Let's work this division problem together. Our division is getting "longer" as the numbers get bigger, but that won't be a problem for you! Watch for the remainder.
Dividing numbers: long division with remainders
Here we go with more long division practice. Ever wonder why we call it "long" division? What's "long" about it, anyway?
Dividing by two digits example 2
Here's another practice example where you divide by two digits.
Level 4 division
Dividing a two digit number into a larger number

Loooong division!

You know your multiplication tables and are getting the hang of basic division. In this tutorial, we will journey into the world of loooong division (sometimes, referred to as "long division", but that's not as much fun to say). After this tutorial, you'll be able to divide any whole number by any other. The fun will not stop!

Lattice multiplication
Introduction to lattice multiplication
Why lattice multiplication works
Understanding why lattice multiplication works

Lattice multiplication

Tired of "standard multiplication". In this tutorial we'll explore a different way. Not only is lattice multiplication interesting, it'll help us appreciate that there are many ways to do things. We'll also try to grasp why it works in the first place. Enjoy!

Partial quotient method of division
An alternate to traditional long division
Partial quotient method of division 2
Another example of doing long division using the partial quotient method

Partial quotient division

Feeling constrained by traditional long division? Want to impress your friends, family and even your enemies? Well, partial quotient division may be for you (or it might not). This very optional tutorial will show you that there are many ways to slice a walnut (just made up that colloquialism).

Multiplication, division word problems: how many field goals?
It's time to start putting to practice the multiplication and division skills you've been building. Word problem fun!
Multiplication, division word problems: how many pieces of pizzas?
How many pizzas, pieces per pizza, and eaten pieces were there? Oh, the questions we must answer! It's enough to make you hungry.
Multiplication, division word problems: pedaling how fast?
Using multiplication and division to make estimates. Easy? Maybe, but what's more important is that you try.

Fancy multiplication and division word problems

In this tutorial, we'll start to challenge you with more sophisticated multiplication and division word problems. If you understand mult-digit multiplication and long division, you have all the tools you need to tackle these. May the force be with you!

Multiplying: understanding by using area models
If you're like us, you're a visual learner. Seeing a multiplication problem visualized using an area model really helps. Check it out!
Multiplying: using an area model
Using graph paper we'll map out an area model to help us with a multiplication problem.

Area models and multiplication

Most of us learn to multiply eventually, but only a select-few actually understand what the multiplication represents. This tutorial, with the help of area models, will allow you to be part of this elite group.