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I. Fill in the blanks:

1. When drawing, the distance between the legs of the compass is 8 decimeters, and the diameter of the circle drawn is (16) decimeters, and the circumference is (50.24) decimeters.

2. Draw the largest circle in a rectangle 6 meters long and 4 meters wide. The area of this circle is () square meters and the circumference is () meters.

3. The radius, diameter, perimeter and area of the circle are enlarged by 5 times, () times and () times respectively.

A wire just forms a circle with a radius of 3 minutes. If it is a square, the side length of the square is () decimeter.

5. A steel wire is 376.8 meters long, just 20 times around a cylinder. The circumference of the cross section of this cylinder is () meters and the radius is () meters.

6. Xiaohua walked four times along the circular flower bed with a radius of 5 meters. He walked () meters in one breath, and the area of this flower bed is () square meters.

7. As shown on the right, the circumference of this semicircle is () cm.

To make this semicircle, you need at least () cm long and wide.

() a rectangle of centimeters.

8. Saw the largest circle from a rectangular board with a length of 5 decimeters and a width of 4 decimeters. The circumference of a circle is () decimeter, and the area of a circle is () square decimeter. The remaining board is () square decimeter.

9. As shown in the picture on the right, it is a ring. It is ().

Graphics, it has () axis of symmetry; If this ring

The circumference of the inner ring is 12.56 cm and the width of the ring is 1 cm, so the outer ring

The radius of is () cm and the circumference is ().

Cm, the area of this ring is () square cm.

Second, choose

1. Considering the number of symmetry axes, the following figure () is quite different from other figures.

A ring, b semicircle and c circle

2. If the area of a semicircular flower bed is 6.28 meters, the perimeter of the flower bed is () meters.

A 12.56 B 6.28 C 10.28

3. As shown on the right, it is a design drawing of a hat (unit: cm).

The radius of the big circle under the hat is () cm.

A 20 B 30 C 40

4. As shown above, it is a design drawing of a hat (unit: cm). To make the annular brim below, you need to use () square centimeters of cloth.

A 1256 B 5024 C 25 12

5. Rectangular pieces of paper are 20cm long and16cm wide. It can cut at most () circular pieces of paper with a radius of 3cm.

A 6 B 8 C 1 1

Third, the judge.

1, the circumference of a half circle is the circumference of a half circle. ( )

2. The circumference of any circle is always π times its radius. ( )

3. The area and circumference of a circle with a radius of 2 decimeters are equal. ( )

If you know the area of a circle, you can determine its circumference. ( )

5. The diameter of a circle is the axis of symmetry. ( )

Fourth, calculation

1, find the area of each circle below.

(1) R = 4 decimeter (2) D = 3 cm (3) C = 25. 12 meter.

2. Find the area of the shaded part. Unit: cm

Five, hands-on operation

1. Complete the operation according to the grid diagram below.

(1) In the figure, the position of each center is represented by several pairs. (3 points)

(2) To move the circle O 1 to the position of O2, you need to first translate the () grid to (), and then translate the () grid to (). (2 points)

(3) Translate 03 down by 2 squares, and then translate it to the left by 7 squares, draw the translated figure, mark the center of the circle, and indicate its position with several pairs in the figure. (4 points)

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Sixth, solve the problem.

1. Build a gravel road with a width of 1 meter around a circular pool with a diameter of 2m. What is the area of this gravel road?

2. A 20-meter-long rope wound around the trunk six times, leaving 1. 16 meters. What is the diameter of this box?

3. Loggers often bundle trees side by side, and then use the floating characteristics of trees to transport them by water, thus saving costs. If 1 0 logs with a diameter of about1m are tightly bound together with iron wire (as shown in the figure), how many meters of iron wire will be used for a circle?

4. As shown in the figure below, the two circles partially overlap. How many square centimeters does the area without overlap differ?

There is a wooden stake in the corner of the rectangular grass (as shown in the picture). A sheep is tied to a wooden fence, if the rope tied to the sheep is 4 meters long. So what is the area of grassland that this sheep can't eat?