Answer:
368 sq. units.
Step-by-step explanation:
We have a square of side lengths 20 units and we cut four congruent isosceles right triangles from the corners of the square.
Now, the four isosceles right triangles have one leg equal to 4 units.
Therefore, the area of four triangles = sq. units.
Now, we have the area of the given square is (20 × 20) = 400 sq. units.
Therefore, the area of the remaining octagon will be (400 - 32) = 368 sq. units. (Answer)