The distance between two opposite corners of the floor is 15.
What is the Diagonal of a Rectangle?
A line segment that connects any two of a rectangle's non-adjacent corners is said to be it's diagonal.
The formula for calculating a rectangle's diagonal length (d) is

where,l = length of the rectangle
w = width of the rectangle
Given, the length of floor (l) = 9 meters
width of the floor (w) = 12 meters
Then, diagonal, 
or, 
or,
Hence, the distance between two opposite corners is 15.
To learn more about the Diagonal of a Rectangle
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