I. Right and wrong issues
1, the position of the circle is determined by the center of the circle, and the size of the circle is determined by the radius of the circle ()
2, the diameter is a line segment with two ends on the circle ()
3. All points on the same circle have the same distance from the center of the circle ()
4. The radius, perimeter and area of the circle are enlarged by four times ()
5. The pi of the big circle is greater than that of the small circle ()
6, two circles with equal areas, the perimeter must be equal ()
7. The longest line segment in a circle is the diameter ()
8. The circumference with a radius of 2 cm has the same length and area ()
9. The circumference of a circle is 3. 14 times its diameter ().
10, the distance between two feet of compasses is 1cm, and the drawn circumference is 6.28cm ().
1 1, pi is 3. 14 ()
12, the diameter of a circle is twice the radius ()
13, the distances from all points on the same circle to the center of the circle are equal ()
14, the areas of two circles with equal perimeters must also be equal ()
15, the circumference of a half circle is equal to the circumference of a half circle ()
16. When the diameter of a circle is enlarged by 10 times, its area is enlarged by 10 times ().
17, a circle with a radius of 2 cm is shorter than a square with a side length of 4 cm ()
18, the circumference of a circle is 3 1.4m, and the circumference of a semi-circle is 15.7m ().
19, square and circle with equal perimeter, and the area of circle is large ()
20, in the same circle, the diameter length is twice the radius ().
2 1, the radius of circle A is three times that of circle B, and the circumference of circle A is three times that of circle B ().
Second, fill in the blanks
1, the circumference is expanded by three times, and the area is expanded by () times.
2. If the radius of a circle is enlarged by 2 times, the area is enlarged by () times.
3. The radius of the big circle is 5 decimeters, and the radius of the small circle is 2 decimeters. Their perimeter ratio is () and their area ratio is ().
4.π represents the multiple relationship between () and () of a circle.
5. When drawing a circle with compasses, the center of the circle determines the circle () and the radius determines the circle ().
6. Cut the largest circle in a triangle with a base of 3 decimeters and a height of 2 decimeters, and the area of the circle is ().
7, semicircle has () axis of symmetry.
8.π is a decimal (), which is the ratio of () and ().
9. A square paper with a side length of 12cm can cut out at most () circles with a diameter of 12cm.
10, the ratio of diameters of two circles is 2: 5, the ratio of perimeters is (), and the ratio of areas is ().
Third, multiple choice questions
1、π()3. 14
A is greater than b and less than c, equal to
2, larger pi () smaller pi
A is greater than b and less than c, equal to
3. On a parallelogram cardboard with a base of 1 1.5 decimeter and a height of 1.5 decimeter, at most () circles with a radius of 15 decimeter can be drawn.
a，3 B，6 C，9 D， 12
4. The diameter of the circle is equal to the side length of the square, and their area ()
A equals b, great circle c, great square.
5, the circumference of a semicircle formula ()
a、 1/2πd B、πr+2r C、πr+r
6. The line segment from the center of the circle to any point on the circle is called ().
A, radius b, diameter c, circumference
7, about the definition of pi is correct ()
Pi is an infinite decimal.
Pi is an infinite acyclic decimal.
Cπ is equal to 3. 14.
D pi is two decimal places.
Third, find the perimeter and area of the following circle:
1, diameter = 3cm.
2.R = 2.4m。
3. d =1.45m.
Fourth, the application questions
1, the minute hand of the clock is 10 decimeter long. How many decimetres did the needle tip of this minute hand walk in 1 hour? How many decimetres do you walk in 20 minutes?
Part of it is made of round iron sheet with a diameter of 3.2 meters. How many square meters does it take to produce 100 such parts?
The diameter of a circle is 3 decimeters. What is its circumference and area?
4. Draw a circle with a radius of 2 cm. What is the circumference? How many square centimeters is the area? Do you feel equal? Why?