Hard
The figure shows a shaded regular polygon inscribed inside a square. If the perimeter of the regular polygon is 8 units then the perimeter of the square is:
For a regular octagon inscribed in a square (corners cut off) with perimeter 8 units, working through the geometry of the cut corners gives the square's perimeter as 4+4*sqrt(2) units.
Re-check your working by substituting the answer back into the original question.