BABY QUILT STARTED

I need to make a baby quilt for my nephew and his wife who are expecting a boy in January.

I bought the fabric quite a while ago.  It's been washed and waiting.

Since I'm into equilateral triangles lately I decided to do another one.

Yesterday I cut out almost all of the triangles.

I finished cutting the triangles this morning, and then after lunch I put together a few rows.

After I got a few rows together I measured it up against the back and the top was wider than the back.  I don't get it - I measured and figured and still got something wrong.

I'll figure it out some other time.  Right now I can't argue with it, it is what it is.

So, I removed the light green outside half triangles and cut down the first triangle on each side.

Now it is the right size.  I'm so confused.  Each triangle is 4" finished, so I figured 10 across and I'd get a 40" wide quilt.  But it ended up wider than the 42" back.  So now it's only 9 triangles wide and and it fits.