4 square units
If you draw a vertical line down the middle of the square, you divide it into two triangles that are congruent to the smaller triangles shown in the figure. Hence each of those triangles has an area of 1/2 square unit.
After you divide the square as as above, you see that two smaller triangles are identical in area to the larger triangles. So, each of those has an area of 2(1/2) = 1 square unit
Then the total of areas is…
2 small triangles + square + 2 large triangles =
2(1/2) + 1 + 2(1) = 4
Hopefully this helps a lot because this was a lot to type!