Mabel, this still happens to me occasionally, after 20 years. However, this is why I took algebra and geometry. I'm gathering you need help because you are changing the size of the quilt from the book/instructions? Then, you need to figure the total number of blocks you will be using. Then, figure the size of each piece in the block by color. So if you need a 4x4 finished size you will need to cut a 4-1/2x4-1/2 piece for that block. Times, for example, 20 for the total number of blocks. You need 20-4-1/2x4-1/2 pieces. From a 40" strip (without selvedge, averaging) you can get 8 pieces (and rounding up for fudge factor). that means you need 3 strips of that color--really 3-1/2 strips but hey! Is this any help?