Need a mathematical genius
 

I purchased the pattern "Poinsettia Stars" that was pictured on the front of Keepsake Catalog a month ago. It is made entirely of HST. Large ones were to be cut 4 7/8 and small ones 2 7/8. I decided to make it easy on myself and cut them 5" squares and 3 " squares. The first block did not match. The second block I was very careful to cut and make the 1/4" seam. Still do not match. Can anyone tell me why?

Your 4 and 7/8 squares would have created 4.5" HST squares. The 2 and 7/8 squares would have created 2.5" HST squares. You probably need to trim down your squares before you use them.

Did you trim down to 4 1/2" & 2 1/2" HST? They should match

yes, they needed to be trimmed. be sure to use a ruler that has a 45 degree line going from corner to corner. lay that on the seam line, trim two sides if needed. turn block and lay ruler on line again and trim last two sides. should fit perfectly after that.

Yes, did you forget to trim them???

You did them the sizes I would have, then I trim them to the right size.

I have a printed page that shows doing 8 at a time, following the lines you draw. That is what I am going to use.
You put your fabric right sides together, draw the lines and keep sewing. Then cut them out. At least I hope this will work for me. I have never added pics or I would put it on here. I could email them to you if you send me a private message.

This is exactly how I trim HST's as well. And those 7/8" cuts are crazy. Use the full inch cutting and trim and everything should match up perfectly.

I agree I never use the 7/8 cut always the full inch then trim

Thank you ladies so much. Those 7/8" cuts are crazy for me.