All three "Powers of 10" puzzles were just math and number systems. No big problem. The Quadrangle Challenge was both a challenge and a simple cipher. The challenge part was having to find at least one geocache in each topo map quad covering Lancaster County. Given how far away I live from Lancaster, I was surprised that I'd already qualified for this challenge. So it was a simple matter of going and finding the final cache.
"Ohm Overload" is probably more of interest to Electrical Engineering folks. (I'm Comp Sci. :) ) In this puzzle, coordinates are derived from the total resistance in two circuits. I knew the formulae from having had Physics class long ago, so all I really needed to do was look up resistor codes and do the math.
"Playfair 6" is a modified Playfair cipher. I decoded the message by hand since there is no software for this Playfair variant yet. However, as I found out, the real puzzle was finding the correct parking lot. It's in an area where none of the parking lots were connected, so I drove in and out a few times until I got the correct one. (I should've studied an aerial photo first.)