Connecting two power supply {LED Light 12v}
You don't want to hook 20 strips end-to-end unless they're making the strips out of much stronger stuff than the ones I have.  Passerby described the math to it.  If you fed three strips from one end of one strip, I wold not be surprised if it burned up the PC traces.

I would run a parallel "bus" and feed strips from both ends.  In Code electrical, 100' is about where voltage drop hits 3% and you want to bump to the next larger wire size. Keep in mind 3% voltage drop at 120V is a 30% voltage drop on 12V! Plug it into a voltage drop calculator and it will do the math.  But the numbers get real scary real fast with 12V at 100'. I asked the calc to show me 12V at 3% voltage drop, and it recommend 3/0 wire (or preferably, 250kcmil aluminum, which is 1/2" diameter). The wire would be bigger than your whole LED strip! 

Now over on diy.se, taking a fat-wire problem and solving it with the thinnest legal wire (14 AWG) is pretty much my "hat".  Here we go:  

One way to solve the long-distance voltage drop problem is to distribute the 12V power supplies along your 100' so you're carrying 120V/230V the long distance instead of 12V. When you double voltage you quarter losses, when you 10x voltage you 1/100x losses. 14 AWG wire would suffice!  tips hat 

This is how light-rail lines do it, they don't carry 600V from Long Beach to Pasadena, they carry 24,000 volts AC and have a 600V substation every 3-5 miles.