Multiplication and division

Multiplying and dividing positive and negative whole numbers, understanding place value, and rounding numbers.

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.
Number line 1
Whole numbers on the number line
Practice skip counting to find a number on a number line with only two tick marks labeled. 
Basic multiplication
Introduction to multiplication
Multiply 1-digit numbers
Multiply two 1-digit numbers. Some problems include multiplying by 10.
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.

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!
Division 1
Introduction to division
Basic division
Divide two numbers.  Quotients are equal to or less than 10.
1-digit division
Divide two numbers.  Quotients are equal to or less than 10.
Example: Expressing division in multiple ways
Dividing Whole Numbers and Applications 1

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.
Multiplying by multiples of 10
Sal decomposes multiples of ten to multiply.
Multiply by tens
Multiply a 1-digit number by a multiple of 10.
Multiplying: 2-digit by 1-digit
Sal solves 32x3.
Multiplying: 3-digit by 1-digit
Sal solves 4x201.
Multiply without regrouping
Multiply 2- or 3-digit numbers by 1-digit numbers. No regrouping.
Multiplying: 2-digit by 1-digit (regrouping)
Sal solves 6x37.
Multiplying: 3-digit by 1-digit (regrouping)
Sal multiplies 7x253.
Multiplying: 4-digit by 1-digit (regrouping)
Sal multiplies 9x8085.
Multiply with regrouping
Multiply 3- or 4-digit numbers by 1-digit numbers. Regrouping (carrying) needed.
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
Multiply 2-digit numbers
Multiply 2-digit numbers by 2-digit numbers. Regrouping (carrying) needed.
Multiplying multiple digit numbers
Sal multiplies 2- and 3-digit numbers using "standard algorithm".
Multi-digit multiplication
Multiply 2-3 digits by 3-4 digits with carrying.
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.

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

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).
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

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!
Division word problem: field goals
Sal solves a division word problem.
Multiplication word problem: pizza
Sal solves a multiplication word problem.
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.

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.
Multiplying with area model: 78 x 65
Sal uses an area model to multiply 78x65.
Multiplying with area model: 16 x 27
Sal uses an area model to multiply 16x27.
Multiply 2-digits numbers with area models
Use an area model to decompose factors and multiply.