Acrobats walk a tightrope on a unicycle. The diameter of the wheel is 40 cm. How many turns does a 50-meter-long steel cable take?
The range of the automatic rotary sprinkler irrigation device on the park lawn is 9M, what is the area it can spray irrigation?
4 Xiaodong measures the circumference of the thickest part of a tree trunk as 125.6cm, and what is the cross-sectional area of the thickest part of the trunk?
1: There is a fish pond with a radius of12m. If there are three fences around this fish pond, how many meters will it take?
12*2*3. 14=75.36 (m) 75.36*3=226.08 (m)
2.a and B leave the same point in a lake at the same time. It is known that the diameter of the lake is 300 meters, the speed of A is 8 1 meter per minute, and the speed of B is 76 meters per minute. So they will meet in a few minutes?
300*3. 14=942 (m) 942/(8 1+76)=6 (min)
Xiaoming goes to school by bike from home. The diameter of the wheel is 0.7 meters. As we all know, the wheel rotates 200 times per minute on average. It takes him 10 minutes from home to school. How far is Xiaoming's home from school?
0.7*3*200=439.6 (m) 439.6* 10=4396 (m)
4. The wheel diameter of a car is 1 meter. If it rotates 400 times per minute, how many minutes does it take to cross a bridge with a length of 2.5 12 km?
2.5 12km = 25 12m 1 * 3. 14 * 400 = 1256(m)25 12/ 1256 = 2(min)。
5: Wrap a rope with a length of 10 cm around a straw 10, leaving 0.58 cm. What is the diameter of this straw?
10-0.58=9.42 (cm) 9.42/ 10=0.942 (cm) 0.942/3. 14=0.3 (cm)
0.3 cm =3 mm
1. The longest line segment in a circle is 6 cm, and the circumference of this circle is () cm.
2. Draw a circle with a circumference of 37.68 cm, and the distance between two feet of the compass should be ().
3. The radius of the circle is enlarged by 2 times, and the circumference is enlarged by () times.
The circumference of a circle is 12.56 cm. After cutting it into two semicircles, the circumference of each semicircle is () cm.
The hour hand of the big wall clock is 60 cm long and the minute hand is 80 cm long. In a day, the total distance that the minute hand tip of this big wall clock passes is () meters.
6. Cut a square iron sheet with an area of 9 square decimeters into a circular iron sheet with the largest area, and the circumference of the iron sheet is () decimeters.
7. After dividing a circle into two equal semicircles, its circumference increased by 6 cm, and the original area of this circle was ().
8. On a rectangular paper with a length of 60 cm and a width of 40 cm, at most () circles with a diameter of 4 cm can be cut out.
9. The sum of the radii of two circles is 6 cm. It is known that the circumference of the great circle is 25.12cm, and the circumference of the small circle is () cm.
10. Draw the largest circle in a rectangle with a length of 10 cm and a width of 5 cm. The radius of this circle is () decimeter.
1 1. The radius of the circle is reduced from 10 cm to 8 cm, and the circumference is reduced by () cm.
12. The sum of circumference, diameter and radius of a circle is 18.56 cm, and the radius of this circle is () cm.