Here's a link to charts and formulas. Scroll down a bit to get to the 4 ata time version. YOu will probably have to make them a bit bigger & cut down. Not sure if 2 3/4 is the raw or finished size.
http://www.blossomheartquilts.com/2012/07/hst-tutorial-and-maths-formula/
I taught math for a short time in SE Michigan, and was told by a couple students they would never need it!