The method of digging and filling is adopted to solve the problem. That is, the large square area minus the rectangular area of the red box.

Solution process solution:

1, the area of the big square is 8×8=64 (square centimeter).

2. The rectangular area of the red border is 7×6=42 (square centimeter).

3. The area of the blackened figure is 64-42=22? (square centimeter)

Topic knowledge point

1, excavation and filling method. Cut-and-fill method is a problem-solving method, which is used in geometric problems, cutting the figure into several regular figures, making the problem easy to solve.

For this problem, it is to fill the black figure into a square figure, calculate its area, then subtract the filled area, and finally get the area of the figure.

2. Square area and perimeter.

Area of a square = side length × side length.

S=a

The side length of a square

Area of square = diagonal x diagonal ÷2. S=d？ ÷2

Circumference of a square =4× side length

C=4a

Square is a special parallelogram and a special rectangle. In the same plane: a quadrilateral with four equal sides and a right angle is a square. A set of rectangles with equal adjacent sides is a square. Diamonds with right angles are squares. The diagonals of a square are equal and bisected vertically.

3. Rectangular area and perimeter.

Area of rectangle = length × width.

S=a×b？

A- the length of the rectangle

B- the width of the rectangle

The circumference of a rectangle =4× (length+width)

C=2(a+b)

A rectangle, also called a rectangle, is a plane figure, but it is a parallelogram with right angles. A rectangle is also defined as a parallelogram with four corners at right angles. A square is a special rectangle with four sides of the same length.

The essence of a rectangle is: two diagonal lines are equal; Two diagonal lines are equally divided; Two groups of opposite sides are parallel respectively; The two groups of opposite sides are equal respectively; All four corners are right angles; There are two symmetrical axes (there are four squares); Unstable (easily deformed); The square of the diagonal length of a rectangle is the sum of the squares of both sides; The quadrilateral obtained by connecting the midpoints of the sides of the rectangle in turn is a diamond.