1. The length of the line segment from the center of the circle to any point on the circle is (). Such a line segment is called a circle ().
2. Draw a circle with a compass with a diameter of 6 cm, and the distance between the two feet of the compass should be () cm.
3.20.4 square meters = () square meters () square decimeter.
A circle has a radius of 4 cm, a diameter of () cm, a circumference of () cm and an area of () cm 2.
5.3.14,227,, π descending order is ().
6. Cut out the largest circle on a square iron plate with a circumference of1.20cm.. The diameter of this circle is () cm, the radius is () cm, and the area is () cm2.
7. Divide a circle with a diameter of 4 cm into several equal parts, then cut it open and put it together as shown below. The perimeter of the combined figure is () cm longer than the original circle.
8. As shown in the figure below, the area of a circle is 6.28 square centimeters, and the largest area of a square in that circle is ().
9. The radius of the great circle is equal to the diameter of the small circle, the circumference of the great circle is () times that of the small circle, and the area of the small circle is () of the great circle.
Second, careful scrutiny and careful judgment (10)
1. The circumference of a circle with a radius of 2 cm is equal to the area. ()
2. The area of the whole circle is larger than that of the semicircle. ()
The perimeters of two circles are equal, and their areas must be equal. ()
When the diameter of a circle is enlarged several times, the area is also enlarged by the same times. ()
5. The ratio of circumference to diameter of a big circle is greater than that of a small circle. ()
Third, repeated selection is more cautious (10 score)
1. The circumference of a circle is () times its diameter. A.3. 14b.6.28c.π。
2. The formula for calculating the circumference of a semicircle is () a.π r b π r+2R2π r
3. The radius of the circle is increased from 1 decimeter to 2 decimeters, and the circumference is increased () A.2 decimeters B.6.28 decimeters C. 12.56 decimeters.
4. The perimeter ratio of two circles is 4: 5, so the area ratio is () a.4: 5b.5: 4c. 16: 25.
5. Three iron wires with the same length are made into rectangles, squares and circles respectively, and () has the largest area. A. rectangle B. square C. circle
Four, careful examination, careful calculation (16 points)
1. Fill in the form carefully (12 points) radius x09 diameter x09 perimeter x09 area 3cm X09X09X09 12 decimeter X09X09X0925. 12 decimeter x09x0993.14 square meters 2. Find out the following figure.
Five, begin drawing calculation (15 points)
1.① Draw a circle with a circumference of 12.56 cm with a compass; ② Draw a radius on the circle and mark the length of the radius; ③ Find the area of this circle again. (5 points)
2. Find the area of the shaded part in the figure below (unit: cm). (5 points)
3. Please draw a square with the line segment (4cm) given below as the edge, then draw two semicircles in the square with two opposite sides of the square as the diameter, then draw a shadow in the square outside the semicircle, and then calculate the area of the shadow part; (5 points)
Six, the use of knowledge to solve problems (3 1 minute)
1. The diameter of a circular mirror is 40 cm. How many square centimeters is its area? How many meters of plastic decorative tape do you need to buy to wrap a circle of plastic decorative tape around the edge of this mirror? (5 points)
2. There is a circular music fountain in front of the children's amusement park, with a circumference of 47. 1 meter. How many square meters does it cover? (5 points)
3. A semicircular water tank cover, its radius is 5 decimeters, and its circumference is how many decimeters? How many square decimetres is the area? (5 points)
Outside a circular flower bed with a radius of 8 meters, there is a circular path with a width of 1 meter. What is the area of this path? (5 points)
5. Divide a circular piece of paper into several equal parts, cut it and make it into an approximate rectangle. It is known that the circumference of a rectangle is 12.42 decimeter. Can you find the square decimeter of this circle? (5 points)
6. The shaded area in the picture is 45 square centimeters. What is the area of this ring? (6 points)
Answer: 1. 1. Equal radius: 2.3.3.20 40 4.8 25.12 50.24 5.3.14 ￠ π ￠ 227 6.30 65438+
Two. XX √×××
Third, China Industrial and Commercial Bank.
Four. 1 (omitted) 2. 124.2 cm 176.625 cm2
Verb (abbreviation of verb) 1 (abbreviated) 2. 1. 14 cm2 3 (abbreviated)
6. 1. 1256 cm2 1.256 m; 2. 176.625 m2; 3.25.7 decimeter 39.25 square decimeter; 4.53.38 square meters; 5.7.065 square decimeter; 6. 14 1.3 cm2.