Placing a comma every three decimal places in numbers with four or more digits is a service to the reader. They simply make larger numbers easier to read by distinguishing the thousands, millions, billions, trillions, and so on, so that we will pronounce the numbers correctly. It can be easy for students to forget the commas or to put them in the wrong places, so Tim Martin came up with a strategy. He says, "Anytime you use the words naked or underpants, kids buy in, so I came up with the Naked Number Dance." The Naked Number Dance is simply 1, 2, 3, kick, 1, 2, 3, kick. Translated to numbers, students start at the right and count 1, 2, 3 as they move over the digits. When they say "kick," they add a comma.
After writing a huge naked number on the board, Tim invited one of his students to come up and put the kicks in. The class did the Naked Number Dance while the student added the commas. Then they read the number together.
On the board: 1 3 7 5 9 2 6 3 9 0 3 2 4
With added kicks: 1, 3 7 5, 9 2 6, 3 9 0, 3 2 4
Don't you love it when teachers make learning fun like Tim does? I know I will think of the Naked Number Dance next time I put commas in a big number: 1, 2, 3, kick.