<p>Girlygirl…
Do you really believe the answer is 4? If you plug in 5 as the side-length of the square, you get the total area as 25. Then since you are given the midpoint of one side, you can determine that the length of that midpoint is 2.5. So the triangle base is 2.5 and the height is 5. The formula for triangle area is 1/2bh, so you get the area for this as 6.25. If you subtract 6.25 from 25, you get 18.75, which is the area of the trapezoid. And now of you divide the area of the trapezoid by the area of the triangle (18.75/6.25) you get 3. Therefore, r=3. Not 4.</p>