Multiply and divide decimals by powers of ten (by 10, 100, 1000 etc.)

In this video I show, first of all, the common shortcut: you move the decimal point in the number as many steps as there are zeros in the number 10, 100, 1000 etc. For example:

2.16 × 10,000 = 21,600.0
It is as if the point moved four steps from between 2 and 1 to between zeros.

You can see better examples of this in my lesson Multiply and Divide Decimals by 10, 100, and 100 at HomeschoolMath.net.

Then, I also show where this shortcut originates, using PLACE VALUE charts. In reality, it's not the decimal point moving (it's sort of an illusion), but the digits of the number move within the place value chart (to the opposite direction from the way the decimal point seems to "move"). This explanation can really help students to understand the reason behind the "trick" of moving the decimal point.

Multiply & Divide Decimals by powers of ten