To find the area and perimeter of a circle, the amount of questions should be larger

Knowing the circumference of the circle, find d= ( find r=( ).

3.The radius of the circle is enlarged by 2 times, the diameter is enlarged by a factor of 2, the circumference is enlarged by a factor of 2, and the area is enlarged by a factor of 2.

4.Annular area (

5.Draw a circle with a compass with a circumference of centimeters, the distance between the toes of the compass should be ( ) cm, and the area of this circle drawn is ( ) square centimeters.

6. The radius of the great circle is 4 times the radius of the small circle, the circumference of the great circle is ( ) times the circumference of the small circle, and the area of the small circle is the area of the large circle ( ).

7. The radius of the circle increases by 1 4, the circumference of the circle increases ( ) The area of the circle increases ( ).

8. The circumference of a semicircle is decimeters, and the area of this semicircle is ( ) square decimeters.

9. Divide a circle into 1000 identical small fans, and cut the circumference of the approximate rectangle 10 cm longer than the original circumference, and the area of this rectangle is ( ) square centimeters.

10. Draw the largest circle in a square with an area of 24 square centimeters, and the area of this circle is ( ) square centimeters; Draw the largest square within this circle, and the area of the square is ( ) square centimeters.

11. The radius of the great circle is 3 times the radius of the small circle, and the area of the great circle is square centimeters, so how many square centimeters is the area of the small circle?

12. The radius of the great circle is 2 times the radius of the small circle, and the area of the large circle is 12 square centimeters more than the area of the small circle, and the area of the small circle is ( ) square centimeters.

13.Find the circumference of the circle.

1)r = 4 dm (2)d 6 cm.

14.Find the area of the circle.

1)r 3 dm (2)d 8 cm.

The outer radius of a ring is 8 decimeters, and the radius of the inner circle is 5 decimeters.

The outer diameter of the bicycle tires is 71 cm, and it rolls 100 times per minute. How many minutes does it take to cross a 1000-meter bridge?

To draw a circle with a circumference of centimeters, the distance between the two corners of the compass is ( ) centimeters.

By dividing the circle into equal parts and cutting it out, you can put together a figure that approximates a rectangle, the length of which is equivalent to the length of the circle ( ) and the width of the rectangle is equivalent to the width of the circle ( ).

The circumference of a circle is decimeter, and its area is ( ) square decimeter.

In a circle, the circumference of the circle is ( ) times the diameter and is the radius ( ).

Among the figures with equal circumference, the largest area is ( ).

Circle, square, rectangle.

Pi is indicated by ( ).

The circumference of the circle The area of the circle is a multiple of the diameter of the circle The circumference of the circle is a multiple of the diameter.

1.All diameters are equal and all radii are equal. （

2. The two ends of the line segment on the circle, the diameter is the longest. （

3. The line segment that passes through the center of the circle is the diameter. （

4. The pi of a small circle is smaller than that of a large circle. （

5. The circumference of the circle is the decimeter, then the circumference of the semicircle is the decimeter. （

1) The radius of a circle is 2 meters, the length of a rectangle is equal to the circumference of the circle, and the width is equal to the diameter of this circle, how much does their area differ? (2) The second hand is 1 cm long, how many centimeters will the tip of the second hand go in 2 hours? (3) The radius of the train's driving wheel is meters, if it turns 300 times per minute, how many kilometers does the train travel per hour?

4) A certain type of washbasin produced by the enamel factory is made of round iron sheets with a diameter of meters, if you produce 800 of this basin per day, how many iron sheets are needed?

The little monkey rides around a circle, and the radius of the circle is known to be 10m, how much m is the circumference of this circle?

A child rolls an iron ring, the diameter of this iron ring is 7dm, how much dm is the circumference?

7* A circle made of cardboard has a diameter of 20cm, and how many square centimeters is the area?

r=20 (divided by)2=10cm

10*10*cm²).

The length of the triangle is 16 decimeters, and what is the calculation of its area.

The circumference of the trunk of a tree is centimeters. What is the area of the cross-section of the trunk in this lesson?

Perimeter = straight meridian * PAI = radius * 2 * PAI area = radius * radius * PAI 1: There is a fish pond, 1, the circle is a kind of ( ) figure on the plane, and the length of the ( ) enclosed in a circle is called the circumference of the circle. At.

, a circle is a kind of ( ) figure on a plane, and the length of the ( ) enclosed by a circle is called the circumference of the circle. In large and small circles, their circumference is always more than ( ) times the diameter of their respective circles, we call this fixed number ( ) is represented by the letter ( ), it is a ( ) decimal number, in the calculation, generally only take its approximate value ( ).

The perimeter is multiplied by the diameter and the area is multiplied by the square of the radius.

Do you provide questions and I answer them, or do you provide questions and answers?

1: There is a fish pond, its radius is 12 meters, if there are 3 circles of fences around this fish pond, how many meters of fence is needed?

12*2*m) m).

2: A and B are walking opposite each other from the same point in a lake at the same time, and the diameter of the lake is known to be 300 meters, and the speed of A is 81 meters per minute, and the speed of B is 76 meters per minute, so the two meet in a few minutes?

300*m) 942 (81+76)=6 (min).

3: Xiao Ming rode a bicycle from home to school, the diameter of the wheel is meters, it is known that the average rotation of the wheel is 200 times per minute, he took 10 minutes from home to school, and asked how many meters Xiao Ming's home is from the school.

m) m) m) 4: The diameter of the wheels of a car is 1 m. If it turns 400 times per minute, how many minutes does it take to cross a kilometer-long bridge?

km = 2512 m 1 * m) 2512 1256 = 2 (min).

5: Wrap a 10 cm long rope around a straw 10 times, and there are still centimeters left, so how many millimeters is the diameter of this straw?

centimeter) centimeter) centimeter).

Centimeter = 3 mm.

1. Fill in the blanks: 1. A circle is a ( ) figure on a plane, and the length of the ( ) enclosed by a circle is called the circumference of the circle. In large and small circles, their circumference is always more than ( ) times the diameter of their respective circles, we call this fixed number ( ) is represented by the letter ( ), it is a ( ) decimal number, in the calculation, generally only take its approximate value ( ).

2. The diameter of a circle is expanded by 5 times, its radius is expanded by ( ) times, its circumference is expanded ( ) times, and the area is expanded ( ) times.

3. Draw a circle with a circumference of centimeters, and the distance between the feet of the compass is ( ) centimeters.

4. Draw the largest circle on a rectangular piece of paper 6 cm long and 4 cm wide, and the radius of this circle is ( ) cm; If you draw the largest semicircle, the radius of this circle is ( ) cm, the circumference is ( ) and the area is ( ).

5. ( It is called the area of a circle. Divide the circle into several equal parts along its radius r, and after cutting, it can be put together into an approximate ( ) The length of this figure is equivalent to the circumference of the circle ( ) is represented by letters is ( ) The width is equivalent to the circle ( ) is represented by letters is ( ) So the area of the circle s (

2. Judgment: 1. The circumference of the circle is a multiple of the diameter of the circle. （

2. The pi of a small circle is smaller than that of a large circle. （

3. Fold a round piece of paper in half several times, and all the creases intersect in the center of the circle. （

4. If the radius of a circle is expanded by 3 times, its diameter will be expanded by 6 times. （

5. The circumference of the semicircle is equal to half of the circumference of the circle. （

6. After a little point, you can draw countless circles. （

1. A bundle of wires is wound 9 times, each circle is 48 cm in diameter, how many meters is this bundle of wires?

2. The outer diameter of a bicycle tire is 60 cm, and the little red cycling wheel rotates 100 times per minute. How many meters per minute does she ride?

3. Which is longer when the sum of the circumferences of two small circles is compared to the circumference of the great circles? (Write out the process in centimeters).

Circumference = straight warp * pai = radius * 2 * pai

Area = Radius * Radius * PAI

Draw the largest circle in a square, and the area of the circle accounts for the area of the square, (this rule is calculated by calculation).

You can directly multiply the area of the square to get the area of the largest circle.