Check out my PowerPoint presentation at my TpT store.
I spend a week on decimals. The first day I introduce the concepts of decimals by relating them to fractions. I use a graphic organizer to help kids grasp the concept and several other activities, which you can check out at my TpT store.
The next day we watch the following video:
Then we review the graphic organizer with more examples. Next I allow them to show me what they know with a worksheet or matching game.
The rest of the week is spent on adding and subtracting fractions. Here is a video that my kids really love and it helps them understand the most important thing when adding or subtracting decimals.