I have been working on volume and area.
With square and rectangles you need to time the length x width. Its the same with a triangle except you have to halve the lengthxx width.
For a rectangular prism and a cube you do L x W x H.
In floor plans their are usually many different shapes like rectangles, squares, semi circles, etc. Also floor plans include finding the area and perimeter of each room and of the whole building. Size means alot in floor plans because you need to make sure your measurements are right.