Using her proportions:
(4) 4" strips each of 9 different fabrics makes a 72"" wide quilt. each 4" strip will give you another 3-1/2"finished, so figure your completed size.
Subtract 72" from the number of inches you need.
Divide the new # by 3.5 (finished block size)
this will give you the additional number of strips, so add to the original number.
Ouch! My brain hurts!