That is a trick question. You described a line that dropped 0.5 inches for every 7 inches. That simply describes a line, not a circle. If you had mentioned that a line intersected a circle, or given some other circle related clue, one could determine the size of the circle. A line that drops 0.5 inches for every 7 inches of run is simply a line with a slope of -0.07143 using the slope formula of (Change in Y) / (Change in X). In this case that is -0.5/7.
