Originally Posted by
Maureen NJ
Sorry. I don’t get that amount. The diagonal of a 9” square is 12.72. There would be 7 across for width (7x 12.72= 89.04”) and 8 for the length (8x 12.72 = 101.76”). 7x 8=56 blocks you would need to make. I use mathopenref.com “diagonals of a square”. If you scroll down, there is a calculator which is a great link.
Your calculation is correct as far as it goes, but misses the blocks in the alternating rows. For example, if you wanted to make a quilt with 2x 2 blocks set on the diagonal, you would need 4 (2x2) plus 1, for a total of 5.
Here, the OP needs 7 x 8 9” blocks (56), plus 6 (which is 7 minus 1) multiplied by 7 (which is 8 minus 1). The plus for the alternating rows is 42 more blocks, for a total of 98. That is the amount Krisb calculated.