I'm not a "math person" either, but I try to think as logically as I can. I use graph paper (google it and choose the size you want -- I use the half inch blocks) I think the layer cakes are 10 inches square. I really don't know how many in the package. First I would figure out how many rows and how many in each row. Then I would figure out the number of blocks in each row X 9.5, and the number of rows X 9.5. That would give you the size of the quilt top. Then I would go to the quilt shop and ask them for batting to fit that size top. (I told you I'm not a math person.
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OK you math people, help us out here! I think "out loud" on graph paper.