16 would be the range. The lowest value is 5, and the highest value is 21. You just subtract those two which gives you 16! (:
Horizontal distance = 48'
difference in elevation = 18"-6" = 12" = 1'
Slope of the sewer line = rise/run = 1/48 = 0.0208 = 2.08%
If the three slashes are 190, 195, and 200, we can see it as
<span>-l----------l--------|--l- with the slightly longer line being around 198.78. Since it is clearly closer to the end of the line than the start of the line, we round it to 200</span>
