Need to calculate several polygon`s average slope

Discussion created by Frikan on Feb 13, 2012
Latest reply on Feb 20, 2012 by Frikan
Hi All
I need to calculate several land parcels average slope and insert it into the attributes table. As a side note I need to do the same for several short line features known as storm water routes?

I have constructed a TIN and created a DEM with the elevations but this is where my knowledge left me and now I am stuck.

Can anyone maybe point me in the right direction? Busy calculating this by hand and it takes ages.