If you have an Easy Angle ruler you can cut your trianles from a 4.5 " strip. I cut a sample triangle from a smaller piece: 4.5 x 5" piece will be just right for ONE yellow triangle finishing 4" high.Also see the following site; scroll down the page to the "printer friendly" button to get a PDF
http://quiltville.blogspot.fi/2013/0...ty-rulers.html
You could do this without a special ruler, too, just remember that starting with a 4,5" high piece (from your yellows the upper point (dog ear)is already cut off and in the other 5"leg it is not cut,