This is how I usually do my math:
5X 8= 40 with 2 inches left. (width of fabric was 42)
1 yard= 36 inches= 5 X7 =35 with 1 inch left
8 (number of blocks in a row) X 7 (number of rows you have in 1yd)=56 blocks from one yard.
56 X 2 (because you have 2 1yrd pieces)= 112 blocks
I hope this was clear!