Originally Posted by
ghostrider
Come at it from the other way. Your 4" cut square is 4" wide by 4" high...or 8" total if you combine them. If you then subtract the 1" of seam allowances, you get 7". Divide that in half (because it's a square and length and width are the same) and you get a 3½" square. Does that help you see it?
If you consider both directions (length and width) for one element (the seam allowances), you have to do it for the other as well (the square sides).
Obviously from a true mathematician! This explanation makes the most sense of all.
Sometimes math--an exact science--just does not seem to make sense.....but it always does! (and this opinion is from a severely math challenged English major!)