2. There is a semicircular glass sheet with a diameter of14cm and a circumference of (21.98cm..
3. In the same circle, the ratio of diameter length to radius is (2: 1).
The radius of a circle is 15 decimeter. If its radius increases by 1 decimeter, its area increases by (3 1) square decimeter.
Draw the largest circle in a square with a side length of 8 cm. The circumference of this circle is (25.438+02) cm.
2. choose.
1.(D) is not a symmetric graph. A. circle B. semicircle C. ring D. parallelogram
2. The diameter of the small circle is 2 cm, the radius of the big circle is 2 cm, and the length of the small circle and the circumference of the big circle are (A).
Answer: One eighth.
3. The radius of the circle is increased from 4 cm to 7 cm, and the area is increased (B). Answer: 9 square centimeters
33 square centimeters
4. The radius of the small circle is 2 cm, and the radius of the big circle is 3 cm. The ratio of the area of the small circle to the area of the big circle is (c). A.2: 3 B.3: 2 degrees Celsius.4: 9
3. Application questions
1. There is a big clock hanging in the school hall. Its minute hand is 40 cm long. How many meters did this minute hand walk all day?
A: The distance traveled by this minute hand one day and one night is 6028.8.
2. After the grenade explodes, the effective killing range is a circle with a diameter of16m. What is the killing area of this Grenade?
A: The killing area of this Grenade is 260.96.
3. The diameter of the train driving wheel is1.5m. If it rotates 300 times per minute, how many kilometers will it travel per hour?
A: The speed is 84.78 kilometers per hour.
There is a street flower bed with a circumference of 28.26 meters. Now, iron railings should be set around the flower bed outside the flower bed 1 m. How long is the iron railing? What is the area of this ring?
Answer: The length of iron railing is 34.54. The area is 94.985 square meters.
5. The radius of the big circle is twice that of the small circle, and the areas of the big circle and the small circle are 12 square meter. What is the area of this small circle?
A: The area of the small circle is 12 square meter.
6. Uncle Liu built a semi-circular chicken farm with a fence 15.7 meters long. What is the area of this chicken farm?
A: The area of this chicken farm is 78.5 square meters.
7. There are two wheels connected by belts. The diameter of the big wheel is 1.5m, and the diameter of the small wheel is 0.5m. If the big wheel rotates once, how many times does the small wheel rotate?
A: Mini wheels have 3 laps.