In a square the length and the width are the same so the fraction (ratio):

 is exactly 1.

The closer to a square a rectangle is, the closer the fraction (ratio)  is to 1.  And we can tell by changing the
fraction to a decimal.

In the case of 4 x 5,



In the case of 8 x 9,



In the case of 10 x 12,



So the closest to 1 is .888888889 or the 8 x 9 rectangle.

Edwin