I. Fill in the blanks (16)

1. The position of the circle is determined by (), and the size of the circle depends on the length of ().

2. Pi represents the multiple relationship between () and () in the same circle, which is represented by the letter (), and the approximate value is () with two decimal places.

3. You can draw () diameters in the same circle; If a circle with a diameter of 10 cm is drawn with a compass, the distance between two feet of the compass should be () cm.

Draw the largest circle in a rectangle with a length of 6 cm and a width of 4 cm. The circumference of this circle is () and the area is ().

5. A circle with a diameter of 6 decimeters, a width of 1 decimeter and an area of ().

6. The diameter of circle A is 8 cm, which is 40% of the diameter of circle B. The circumference of circle B is ().

7. If the radius of the big circle is equal to the diameter of the small circle, the area of the big circle is () times that of the small circle, and the circumference of the small circle is () times that of the big circle.

8. Draw a circle with a radius of 4cm in a rectangle with a length of 32cm and a width of16cm. You can draw at most () such circles, and the sum of the areas of these circles is ().

Second, the judgment question. (8 points)

1. The circumference of a circle is π times the diameter. ( )

2. The diameter of the circle has been expanded by four times, and the area of the circle has also been expanded by four times. ( )

The circumference of a circle with a radius of 1 cm is 3. 14 cm. ( )

The circumference of a circle is 12.56 cm and the area is12.56cm 2. ( )

5. The radius of the circle increased from 6 decimeters to 9 decimeters, and the area of the circle increased by 45 square decimeters. ( )

6. The longest segment in a circle is the diameter. ( )

7. A circle is an axisymmetric figure, which has numerous symmetry axes. ( )

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

Three. Choice (9 points)

1.3. 14( )π

A. = B. > C. & Ltd. Not sure.

2. When the perimeters are equal, the largest area is ()

A. parallelogram b rectangle c square d circle

Fourth, calculate the perimeter of the following circle. (8 points)

1. The diameter is 6 square centimeters. The radius is 5 decimetres.

5. Calculate the area of the following circle. (8 points)

1. The radius is 8cm2. The circumference is 9.42m (π is 3. 14).

Six, the application problem (1 problem 8 points, the rest of each question 6 points)

1. A wire can form a circle with a radius of 3 cm. If this line is re-enclosed into a square, what is the side length of this square?

2. Enclose a cylindrical grain depot with mats. The ground circumference is18.84m. How big is the grain depot?

3. A factory club has a circular dance floor with a circumference of 37.68 meters. Now it is planned to widen the perimeter by 1 meter. How much can the dance floor area be increased?

4. Two pulleys are connected together. The diameter of the big pulley is 0.54m, the radius of the small pulley is 0.09m, and the big pulley rotates five times. How many turns does the small pulley turn?