The formula that relates the length of a ladder, l, that leans against a wall with distance d from the base of the wall and the height h that the ladder reaches up the wall is l = startroot d squared + h squared endroot. What height on the wall will a 15-foot ladder reach if it is placed 3. 5 feet from the base of a wall? 11. 5 feet 13. 1 feet 14. 6 feet 15. 4 feet.