Fill in the blanks.

1, draw a circle with a compass, and the distance between two legs of the compass is the drawn circle (). In the same circle, the ratio of diameter to radius is ().

2, a semicircle balcony, diameter of 4 meters, its area is ().

3. The radius of the big circle is equal to the diameter of the small circle. The circumference of a small circle is () of the circumference of a big circle, and the area of a small circle is () of the area of a big circle.

4. The radius of a circle is 18cm, the radius is enlarged by 5 times, the diameter of the circle is enlarged by () times, the circumference is enlarged by () times and the area is enlarged by () times.

5. There is a circle with a radius of 4 decimeters, its area is () square decimeter, and the area of this circle is () square decimeter, which is () square centimeter.

6. The diameter of a circle is 3 cm, and the area of a semicircle is ().

7. If the radius ratio of two circles is 2: 3, their perimeter ratio is () and their area ratio is ().

8. Divide a circle into several equal parts, and then cut it into an approximate rectangle. It is known that the width of a rectangle is 2 cm and the length of a rectangle is ().

Second, the judgment question.

1, a little bit can draw countless circles. () 2, two semicircles can be spelled into a whole circle. ( )

3. The line segment from the center of the circle to any point on the circle is the radius of the circle. ( )

4. When r=2 cm, the circumference and area of the circle are equal. ( )

5. Cut exactly two circles with a radius of1.5cm in a rectangle. The area of this rectangle is at least 18 square centimeter. () 6. The circumference of a semicircle is exactly half that of a circle. ( )

7.r2 stands for r×2. () 8. The circumference of a circle is one centimeter, and the circumference of a half circle is one centimeter.

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

Third, multiple choice questions.

1, two circles with different sizes, whose radii increase by 2 cm each, which circle's circumference increases much? () ① There are as many big circles ② as there are small circles ③.

2. Draw the circle into an approximate rectangle. The following statement () is correct.

① perimeter changed, area unchanged ② perimeter unchanged, area changed ③ perimeter and area unchanged.

3. Two pulleys are connected together, one of which has a diameter of 6 decimeters. When the other wheel turns once, it turns three times, and the diameter of the other wheel is () decimeter. ①2 ②3 ③6 ④ 18

4, a 6 cm long wire into a square, and then into a circle, their area relationship is (). 1 equal; ② The square area is large; ③ Great circle area.

5. Cut the circle into two semicircles along its diameter. At this time, the perimeters of the two semicircles are compared with the original circle (), and the areas of the two semicircles are the same as the original circle ().

① Decrease ② Increase ③ Equal ④ Uncomparable.

6. For tractors, the diameter of the rear wheel is twice that of the front wheel. If the rear wheel rolls 6 times, the front wheel rolls () times. ①3 ②6 ③9 ④ 12

7. Draw the largest circle in a square with a side length of 5 cm, and the area of the circle accounts for () of the square.

① ② ③ ④

8. For a circle with a circumference of 15.7 cm, when drawing a circle, the distance between two feet of the compass is ().

① 2cm, ② 2.5cm, ③ 4cm, ④ 5cm.

Round unit exercise 2009- 12-05 09:38:25| classification: cet-6 | label: | font size, large, medium and small subscriptions.

First, complete the table below.

Radius r of a circle

Diameter d of a circle

Circumference c of a circle

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 (), the area is () and 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.

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. ( )

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

1，pi () 3. 14。 A, greater than B, equals C, less than.

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

A, isosceles triangle b, square c, circle

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?

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?