I need your help...I have some 10 1/2" applique blocks that I want to make into a sawtooth block. You know....just to add the flying geese and the corner squares on to the appliqued block. But, how do I determine the sizes of these additional pieces. I KNOW someone on here knows how to do the math. LOL Thanks.

If I correctly understand what you are saying, I find it easiest to "sawtooth border" a block using HST rather than Flying Geese. For a 10.5" appliqued square I would use 2 1/2 unfinished HST (finished size would be 2" once all sewn in). You would use 5 of these on each side and can put a plain square in each corner. The plain square should also be an unfinished size of 2 1/2"

@feline
I'm reading the OP as wanting to put the applique block in the CENTER of the Sawtooth.

@misoop
The sawtooth is a 4x4 grid, so if you want to use your blocks in the center, then the borders will be 5"(finished) each. The completed block will be 20"(finished).

Cutting instructions:
Corner squares - CUT 5.5"
Flying Geese - CUT rectangles 10.5" and the squares 5.5"
(use this method for construction http://www.quilterscache.com/S/SawtoothBlock.html)

I prefer the Flying Geese method but you can also opt to make 8 HST's that come out 5.5" unfinished. Cut the squares 6.25", put 2 fabrics right sides together, sew once, diagonally, cut either side, blah, blah, blah, and then trim them down to 5.5" ;)

Ahh a sawtooth star! Now I get it. Thanks. Now the flying geese make a lot more sense to me and I would do it exactly as MTS describes. Easiest way.

MTS, that's what I meant. Thank you for this information. I didn't realize that the block would turn out this large. I think I'll "practice" with the same dimensions on some scrap fabric and see what I think. Thanks sooo much!!