In the diagram at the left, we see 6 full unit squares inside the triangle.
But, we do not know how the other unit squares have been divided. They are not cut along their diagonals which would cut them in half.
Since this is a right triangle, we can create a rectangle around the triangle such that our triangle is half of the rectangle in area.
Area of rectangle = 18 square inches.
Area of triangle = **9 square inches. ** |