# Cut the disk with a hole in four equal pieces

Cut the shape below in four congruent pieces. The gray area is a hole. In non-mathematical terms, cut the white area in 4 pieces having the same shape, same size, possibly mirrored or rotated.

Note: the hole is not randomly placed. It is in the exact size, shape and position where it needs to be for the solution to work.

• Do we need to know anything more about the hole? It looks like it's horizontally symmetric, with a linear top edge and circular left and right edges; is that accurate? Do we need to assume that the vertices form an equilateral triangle, or that the center of a circular arc is the opposite vertex? Nov 12, 2014 at 23:15
• For those with little knowledge of maths, what is 'congruent' exactly? Same form, same size... Nov 12, 2014 at 23:30
• A quick google says: Geometry (of figures) identical in form; coinciding exactly when superimposed. Nov 12, 2014 at 23:32
• @MartynA I think you need to look at Jonathan's answer more carefully. Nov 13, 2014 at 12:12
• Ah! I beg your pardon. Nov 13, 2014 at 12:14 