How many different addition number sentences can you write with a total of 7? Join Mr. Hammer for this lesson as we use cube trains to write number sentences with a total of 7! For this lesson, youâll need seven objects that students can move around and count, along with a pencil and paper or whiteboard and dry erase marker. If you have access to a workbook, or a printer, we also suggest accessing the Problem Set and lesson template available using the links below the video.