Numbers and Operations Teacher Resources

In this video, a complex number is defined and graphed on the complex plane. Sal also shows how to add, subtract, and multiply two complex numbers. He starts showing how to divide two complex numbers, but runs out of time and continues...

In this video, a complex number is defined and graphed on the complex plane. Sal also shows how to add, subtract, and multiply two complex numbers. He starts showing how to divide two complex numbers, but runs out of time and continues...

This video continues looking at dividing complex numbers by looking at the conjugate of a complex number. The instructor then uses the conjugate to rationalize the denominator of a rational expression with a complex number in the...

This video continues looking at dividing complex numbers by looking at the conjugate of a complex number. The instructor then uses the conjugate to rationalize the denominator of a rational expression with a complex number in the...

First demonstrating the improper ways of solving an equation (left-to-right, multiplication first), Sal shows viewers how the answer of an equation can be drastically incorrect by neglecting to use the order of operations. He uses...

Demonstrating a "really hairy and beastly problem," Sal again shows the power and importance of solving an equation according the order of operations. Additionally, he guides viewers through a step in the equation when there are multiple...

Please Excuse My Dear Aunt Sally - or whichever mnemonic your students use for the order of operations - is the focus of this video. Sal takes viewers through various mathematical equations which require the use of the order of...

Before Sal can divide a mixed number, he has to rewrite it as an improper fraction. He explains that dividing a fraction is the same as multiplying it by its reciprocal and that you can "cancel out" numbers to make multiplying easier.

Adding double-digit numbers can seem difficult for some students. But, this Khan Academy video makes this process clear in a developmentally sound way. Students watch as 'Sal' adds the number 46 to 43. He references each number by its...

Deepen the number sense of your math class with a short presentation on writing equations. Using the relationship between numbers, young mathematicians learn how to determine the missing operator in an equation. A number of opportunities...

Are your students learning about solving word problems involving multiplication? If they are, then this video could be a perfect complement to your lesson. Sal shows students how to use rounding to estimate the product of a double-digit...

Two very similar numbers and you have to figure out which one is larger. The teacher diagrams a place value chart and shows you how to write the two numbers to make a comparison.

So you want to put some given values in order from greatest to least? The instructor starts out by drawing a place value chart. She then inserts all the numbers into the chart. This helps you visually see their value so you can compare...