First, complete the table below.

Radius r diameter d perimeter c area s of a circle.

2 cm

2 cm

18.84 cm

8 cm

Second, think about it and fill it out.

1. When the distance between two feet of the compass is 4 cm, the circumference of the circle drawn is () cm.

2. Draw the largest circle on a rectangular paper with a length of 8 cm and a width of 12 cm. The diameter of this circle is () and the area is (

), the circumference is (

)。

3. The diameter of a wheel is 55 cm, and the wheel rotates once, about () meters forward.

4. The diameter of the outer circle of a ring is 10cm, the diameter of the inner circle is 8cm, and the area is () cm2.

5. The radius, perimeter and area of the circle are enlarged by 2 times, () times and () times respectively.

6. A circle is surrounded by a (). A circle is a () figure with a () axis of symmetry, and any straight line () of the circle is the axis of symmetry of the circle.

7. A circle has a diameter of () and a radius of (). () is called the diameter, and is represented by the letter (); () is called the radius and is represented by the letter ().

8. All () in the same circle are equal, and all () are equal. In the same circle, () is twice as much as (), and () is (). The formula is: (or).

9. The center of the circle determines the circle (), and the distance between two feet of the compass is (). The position of the circle is related to (), and the () of the circle is related to the radius.

10, of all the line segments in the circle, () is the longest. Among (), only () which crosses () is the longest.

1 1. Cut out the largest circle with a square paper with a side length of 10 cm. The diameter of this circle is () and the radius is ().

12, the distance from any point on the circle to the center of the circle is ().

The same circle has a radius of 5cm and a diameter of () cm.

13. A circle is a () figure on a plane.

14, the radius of the circle is 3cm, the diameter is () cm and the circumference is () cm.

15. The circumference of a circle is 28.26 meters, the diameter is () cm and the radius is () cm.

16, the minute hand of a clock is 6 cm long, and it ran twice and walked () cm.

17。 The circumference of a circle is 12.56 cm. If you draw this circle with a compass, the distance between two feet of the compass is () cm.

18, a circle, the radius of the outer circle is 3cm, the radius of the inner circle is 2cm, and the area of this circle is () 8. A sector area with a central angle of 90 degrees is a circle area ().

Third, please be a small referee.

1, the center of the circle determines the position of the circle, and the radius determines the size of the circle. ( )

2. When the radius of a circle is equal to 2 decimeters, the circumference and area of the circle are equal. ( )

The area of a circle is equal to the area of a square, and their perimeters must be equal. ()

4. The diameter of the same circle must be twice the radius. ( )

5. The diameter of the line segment with two ends on the circle is the largest. ( )

6. The circumference of a semicircle is half that of a circle. ( )

7. The distance between two feet of a compass is the diameter. ( )

8. The radius must be smaller than the diameter. ( )

9. The radius of a circle is the diameter. ( )

10, the line segment with both ends on the circle must be the diameter. ( )

1 1, and the center of the circle is related to the size of the circle. ( )

Fourth, choose one. (Choose the serial number of the correct answer and fill in the brackets)

1，pi () 3. 14。

First, greater than

B is equal to

C, less than

2, in the following figure, the symmetry axis is the most ().

I. isosceles triangle

square

C, round

3. The circumference of a circle is 3 1.4 decimeter, and the area of this circle is () decimeter 2.

a、3 14 B、78.5 C、 15.7

4. A semicircle with a radius of r and a circumference of ().

a、πr + 2r B、πr C、π/4

5, square, rectangle and circle with equal perimeter, () has the largest area.

A, square b, rectangle c, circle

Fifth, do as required.

1. Please draw a circle with a compass with a diameter of 3 cm.

Please draw the symmetry axis of the picture below.

6. Calculate the area below.

Seven, solve the problem.

1. The minute hand of the watch is 5 cm long. What is the distance traveled by the minute hand tip in 2 hours?

2. The bowling radius is about 1dm, and the fairway length is about 18m. How many times should bowling be rolled from one end to the other?

3. A flower bed with a diameter of 5 meters is surrounded by a circular path with a width of 1 meter. What is the area of this path?

4. There is a circular lawn with a circumference of 62.8 meters, and it is ready to install an automatic rotary sprinkler irrigation device for sprinkler irrigation. There are three types of devices with a range of 20m,15m and10m. Which do you think is more suitable? Where is it installed?

The circumference of a circle is equal to that of a square. The side length of this square is 6.28 cm. How many square centimeters is the area of this circle?

6. Circular pool, with circumference of 18.84m and area of how many square centimeters?

7. With a diameter of 1.5m, the roller rotates 8 times per minute, and how many meters does it advance per minute?

8. The round fish pond is 4m in diameter. What is the circumference of this fish pond?

9. The radius of automatic rotary sprinkler irrigation device is10m, and its maximum sprinkler irrigation area.

How many square meters is it?

10. The circumference of the lawn is 50.24 meters. How many square meters is this lawn?

Just try it. ※.

There is a plum flower bed in the center of the square, and the outer circle is five semicircles, each with a radius of 2 meters. What is the circumference of this flower bed?