keep in mind your pattern could also be wrong. If you want to end up with a FINISHED 3" 9P block (3 1/2" unfinished) you should cut your strips at 1 1/2". Then sew your strip sets (light dark light and dark light dark). Cut your strip sets into 1 1/2" units and then sew three together for your 9P. This will give you a finished 3" 9P.