Every number here is a working estimate to check with your building authority. Whoever prints this page takes responsibility for what is in it.
Ramps and door landings
Ramps, slopes and door steps. 4 lessons.
Slope sets ramp length. Guess first. Guess how far the ramp reaches, then change the slope and watch it. 
Folding a ramp to fit the yard. Change it. Fit this ramp inside the yard. 
The step down from the door. Try options. Lower the deck below the door and see what the door needs. 
Ramps to an upper deck. Guess first. Guess how much ramp a deck 9 ft up needs, then try it.