For our soils unit, we spend a day outside determine slope of a site. This is a very rudimentary activity, but it is outside and uses math. I bought a pack of surveyor's flags and wrote on them the distance between them (not actual) and the elevation of each above sea level (again, not actual elevation). I use really basic numbers so it is not confusing while trying to understand the concept. I place these flags out on the practice football field right outside my door using the hill to mimic slope. They use the formula rise/run=slope or "rise over run". Rise is the change in elevation and run is the distance between the flags. I spread out the flags so the students can't look at each others work and they have to rotate in a circle. I have kept the same flags for several years and pull them out on a nice day during the soils unit. I have included a worksheet with the numbers I use (with answers!) and a couple pictures. Not an original idea of mine, I stole it from a "veteran".