Answer
312.5 $ft^{2}$
Work Step by Step
Make the diagram of a square, and find the area.
A=bh
A=25(25)
A=625
Find the area of the white region of the square you formed.
A=$\frac{1}{2}$bh
A=$\frac{1}{2}(25)(25)
A=312.5
Subtract the area of the triangle from the area of the square:
625-312.5=312.5