Glad you got it figured out, Suern3.
I took college level trig when I was a senior in high school. In college I did class after class of statistics, doing it by hand even though computers had been invented by then! I worked with engineers, I did payroll, I did all sorts of math in my head.
Then when I was about 40 I started losing my math abilities. Don't know if it is aging, my medications, or what but stuff that used to be super easy and done in my head I can barely do on paper any more. I'm still pretty darn good with a calculator. But at 60, I am definitely getting more and more math challenged and I'm doing more and more by charging ahead and seeing what comes out.
While I prefer extra wide fabric for backs, I can't always afford it. For whatever reasons I am fundamentally unable to make a quilt be less than a width of fabric, just can't do it... even if I can, then the back I want to use is only 40 usable inches or whatever and not the full 44" I need.
As time has gone on, I do more and more piecing of my backs rather than less because I like it and it allows me to use fabrics I collected for the top but didn't use there, or a good place for large scale prints. For the same reason I typically use a slightly wider than standard binding and sometimes even piece the binding, it's one last place I can add fabrics!