Question: what is the slope of the line that is perpendicular to k?
Answer: Line k is perpendicular to line m. What is the slope of line k? To find the slope of a line perpendicular to a given line, we must take the negative reciprocal of the slope of the given line. Thus the slope of line k is the negative reciprocal of 2/5 (slope of line m), which is -5/2.