formulas for rectangles and areas I have a certain side ratio of small rectangle, and a side ratio for a large rectangle. How can I write an equation that gives me the number of small rectangles that will make the large rectangle? Is  there a formula for that?
Apologies for the title -- it was a last-ditch attempt.

I think that you might mean you have the ratios $x$ = (side 1 of small rectangle)/(side 1 of large rectangle) and $y$ = (side 2 of small rectangle)/(side 2 of large rectangle), in which case your problem is solvable. The area of the small rectangle is (side 1 of small rectangle)(side 2 of small rectangle) and the area of the large rectangle is (side 1 of large rectangle)(side 2 of large rectangle), thus (# of small rectangles it takes to cover large rectangle) = (area of large rectangle)/(area of small rectangle) = ((side 1 of large rectangle)(side 2 of large rectangle))/((side 1 of small rectangle)(side 2 of small rectangle)) = $(1/x)(1/y)$ = $1/(xy)$.
