Question 67115
Well, slope is rise/run.
Instead of doing rise, why don't you take the 1,800 feet descended and divide that by the the amount of feet in 3.25 mi.

So:
5,280 ft = 1 mile
5,280 x 3.25 = 17,160

Then divide:
1,800/17,160

What do you get?
=.1048951048951048951048951048951...
but what you're looking for is:
10/100 or 1/10
meaning for every 1 foot down you are going 10 feet horizontally. :)