Question 268506
One way to explain it is:
If you are driving down a 12% grade, You will aways be 12%
below where you would have been if you could have 
driven on flat ground from where you started.
Say you descend 2 ft. You are 12% below what?
{{{2 = .12x}}}
{{{x = 2/.12}}}
{{{x = 16.67}}} ft from start
That's how far you would have driven on flat ground
Say you descend 20 ft. You are 12% below what?
{{{20 = .12x}}}
{{{x = 20/.12}}}
{{{x = 166.67}}} ft from start
That's how far you would have driven on flat ground
Say you decend 2000 ft. You are 12% below what?
{{{2000 = .12x}}}
{{{x = 2000/.12}}}
{{{x = 16666.67}}} ft from start
Also how far you would have driven on flat ground
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Suppose you are on a 1% grade and you descend 2000 ft.
If you had been on flat ground from the start, you
would have driven:
{{{2000 = .01x}}}
{{{x = 200000}}} ft from start
The same thing works for hills, too
If I'm on a 1% grade going uphill, and I gained 2000 ft
vertically, where would I be if I had driven on flat ground?
{{{2000 = .01x}}}
{{{x = 200000}}} ft from start -the same answer, but now I'm
looking down at where I started, instead of looking up.
Hope this helps.Drawing pictures is a good idea, too