Oh oh, I forgot to tell how many 8 1/2" blocks to cut. 10x11 (10rows by 11 columns of 8 1/2' blocks. So you multiply 10x11=110. So you will cut 110 (maybe a few extra) 8 1/2" blocks. 110 blocks that need 2 1/2 square in each corner. So you would multiply 110 x 4 = 440 small squares. 1 jelly roll strip will give you 17 small squares. (43"/2.5"). 16 small squares if the jelly roll strip is 42". So if you need 440 small squares - divide that by 16 and you will have the amount of jelly roll strips that are needed. 440/16=27 or if jelly roll is 43" then it would be 440/17=25.
Hope this is clearer than mud.