A  Simple but Powerful Example of Contextualized Mathematics

Below is an activity provided by Dave Pfortmiller.  This activity could be used in either Geometry in Construction or AMPED.  Thanks Dave.
What is the slope of the vent stack?
What is the slope of the Main sewer line drain?
What is the slope of the floor?
What is the slope of the vent from the bathtub?
What is the slope of the toilet drain?
What is the slope from the sink vent?
What is the slope of the sink drain?