To calculate the grade of a road, you can use the formula: grade = (rise / run) * 100, where rise is the vertical change in feet and run is the horizontal change in feet.
In this case, the rise is 27 ft and the run is 100 ft. Plugging these values into the formula, we get:
grade = (27 / 100) * 100
grade = 27%
Therefore, the grade of the road that rises 27 ft for every 100 horizontal feet is 27%.