Pinwheel dilemma

Someone came to me this week with a, new to me, way to make pinwheels or just half square triangles in general. You start with your two squares cut to the size you want for your unfinished pinwheels to be.  In my case I tried 3 1/2". Now sew 1/4" around all of the outer edges

                 

Next cut the square in half, twice on the diagonal.

         

Open up the half square triangles, press and sew together. Believe it or not it comes out 3 1/2" square.

I was a little skeptical that I could truly get the same size as the square I started with, the math just didn't seem to make sense to me. Although, to think about it a square on point does take up more space then one set square.

        

Usually I make mine by adding 7/8" to the finished size of the half square triangle I need, in this case 

2 3/8" for the squares. Draw the diagonal line on the wrong side and sew 1/4" on either side of the line. Cut apart on the line. I would need two sets of squares to make the four sections of the pinwheel.

Only real disadvantage I can see, to this, new to me method, is that all the bias is to the outside of the square. So you will need to be careful not to stretch it as you handle it and piece it in. But you do seem to save fabric and maybe even time.

Guess I will be using this method a little more often.  Thanks Mindy, for challenging me with this method.