[Solved] Find size of rectangles to fill area

As far as I understand, you want to place n rectangles with fixed C=W/H ratio on the wall with given Width and Height

Let rectangle height is h (unknown yet), width is w = C * h

Every row of grid contains

 nr =  Floor(Width / (C * h))   // rounding down

Every column contains

nc = Floor(Height / h)

Write inequality

n <= nc * nr
n <=  Floor(Width / (C * h)) * Floor(Height / h)

and solve it (find maximal possible h value) for unknown h

For real values of parameters h might be found getting initial approximate value:

 h0 = Ceil(Sqrt(Width * Height / (n * C)))

and decrementing h value until inequality becomes true