1. A circular garden, with a diameter of12m, is surrounded by a 2-metre-wide path with a fence on the outside. How long is the fence?
2. The circumference of a rectangle is equal to the circumference of a circle with a radius of 25 decimeters. It is known that the length of the rectangle is 4 meters, and the area of the rectangle is how many square meters?
4. The front wheel diameter of the stroller is 0.28m, and the rear wheel diameter is 0.35m.. 70 laps for the front wheel and how many laps for the rear wheel?
6. The circumference of a circular playground is 62.8 meters, and the back radius is reduced by 1 meter. How many meters has the circumference been reduced?
3. The radius of the circular garden is 3m, and fences are set around the garden. How long is the fence?
The outer diameter of bicycle wheel is 70cm. How many centimeters can 10 minute be made if it rotates 120 times per minute on average? How many meters?
1.π=3. 14。 ( )
2. The radius of the circle is quadrupled, and the circumference of the circle is quadrupled. ( )
If the perimeters of two circles are equal, then the areas of the two circles must be equal. ( )
A circle with a radius of 2 cm has the same circumference and area. ( )
1. The circular iron ring has an outer diameter of 40cm and an inner diameter of 20cm. How much iron does it take to make such an iron ring?
2. A big clock, the hour hand is 5 minutes long and the minute hand is 7 minutes long. After an hour, how many decimetres did their tips turn?
3. A round fish pond with a diameter of 4 meters. What is the circumference of this fish pond? How many square meters does it cover?
4. The sand pile occupies a circle on the ground, and the length of one week is 15.7 meters, so what is the diameter?
5. The radius of the bicycle wheel is 40cm, and the wheel rotates 100 times per minute. How many minutes does it take to cross the 25 12m bridge?
6. The diameter of the circular garden is16m, and three-eighths of them are planted with roses. How big is the area where roses are planted?
1. The outer diameter of the bicycle wheel is 0.6m.. Xiaohua rides a bike from home to school. If it rotates 100 cycles per minute, it takes him 10 minutes to get from home to school. How far is Xiaohua's home from school?
2. The outer diameter of train wheels is 0.9 meters long. If it rotates 400 times per minute, how many kilometers does the train advance per hour?
The outer diameter of bicycle tire is 70 cm. If the wheel rotates 100 times per minute on average, how many meters can it walk in half an hour?
A circular garden is 8 meters in diameter, and three quarters of orchids are used. What is the planting area of orchids?
5. What is the length and area of the largest circle after cutting on a square paper with a side length of 10 cm?
6. Cut out the largest circle on a square cardboard with a circumference of 4 cm. What's the remaining area?
8. Cut the largest circle on the tin foil, which is 8 decimeters long and 5 decimeters wide. What is the chip area?
10. A circular ring, with an outer diameter of 30 cm and an inner diameter of 10 cm. What is the area of this ring in square centimeters?
12. The water tank mouth is a circle with a diameter of 0.75 meters. Make a wooden cover for this water tank, and the diameter of the wooden cover is required to be 5 cm larger than that of the cylinder mouth. How many square centimeters is the area of the wooden cover?
14. A semi-circular chicken farm was enclosed by a fence of 18.84 meters. What is the area of this chicken farm?
16. Build a 2-meter-wide gravel road around a circular pool with a diameter of 6 meters. What is the area of this gravel road?
17. Pave a path with a width of 1 meter around a circular pool with a diameter of 8m. What is the area of this path?
18. A wall clock with an hour hand 40 cm long. After a day and a night, how many square centimeters did the hour hand sweep?
3. Build a gravel road with a width of 1 m around a circular pool with a diameter of 2m. What is the area of this gravel road?
1. The areas of two circles with equal perimeters must also be equal. ( )
2. Square and circle with equal perimeter, and the area of circle is large. ( )
The area of a circle with a radius of 2 cm is equal to its circumference. ( )
If the area of a circle is equal to the area of a square, the circumference of the circle is shorter than that of the square. ( )
5. Compared with two circles, the area of the circle with smaller circumference must be smaller. ( )