Place value and large numbers up to trillions (6th grade math)

In this video, I teach the basics of place value and large numbers with up to 15 digits. We group the digits of large numbers in groups of three, called periods. So, a number might have a trillions period, billions period, millions period, thousands period, and ones period.

A large number can be written in expanded form, which means writing it as a sum of its "parts". It's easiest to write these sums using powers of ten.