Rectangle A
24 sq units
4 × 6
Rectangle B
6 sq units
3 × 2
Total floor
30 sq units
24 + 6 = 30
Total = Rectangle A + Rectangle B
An L-shaped room is just two rectangles. Drag the dots to set the overall width and height, and the bite taken out of the top-right corner. Split it along the faint line, work out each rectangle, then add them up.