First, the roll surface is 3 points.

2. Fill in the blanks: 28 points

1. When drawing a circle, the distance between the two legs of the compass is 4 cm, so the diameter of the circle is (8) cm, the circumference is (25. 12) cm and the area is (50.24) cm 2.

The circumference of a circle is more than three times its diameter. This multiple is a fixed number. We call it (pi), which is usually represented by the letter (π). It is a (infinite cycle) decimal, and taking two decimal places is (3. 14).

3. A circle is an (axisymmetric) figure with (countless) symmetry axes. A semicircle has (1) symmetry axes.

Divide a circle into several parts evenly, and you can spell an approximate rectangle. The length of a rectangle is equivalent to a circle (half the circumference) and the width is equivalent to a circle (radius), so the area of a circle is s = (π r 2).

Draw a circle with the length of 18.84 decimeters, the radius of the circle is (3 decimeters), and the area inside the circle is (28.26) square decimeters.

6. Cut out the largest circle on a rectangular cardboard with a length of 8 cm and a width of 5 cm. The area of a circle is (0. 19625) square decimeter.

7. (Radius) determines the size of the circle and (Center) determines the position of the circle.

8. If the radius of a circle is doubled, its circumference is doubled and its area is doubled.

9.1/5 = (20)% = (8) ÷ 40 = 4: (20) = (0.2) (fill in decimal places)

10, A number is 50, B number is 30, and A number is (66.7 )% more than B number.

1 1, 60% of (5) kilometers is 3 kilometers; 20%( 32) tons less than 40 tons.

Iii. Judgment: 12.

1, the diameter is always greater than the radius. (10)

2. The circumference of a semicircle is the circumference of a circle divided by 2. (10)

3. The symmetry axis of a circle is the straight line where the diameter lies. ( √ )

The circumference of a circle is 3. 14 times the diameter. (10)

5. A circle with a radius of 2 cm has the same area and circumference. (10)

6. A dress is sold at 7.5% of the original price at a discount of 25%. (10)

Fourth, multiple choice questions. Fill in the serial number of the correct answer in (). 14 point

1, the areas of two circles are not equal, because (c)

A, pi is different; B, the position of the center of the circle is different; C, the radius is different.

2. The perimeters of two circles are equal, so the area of these two circles is (c).

A, not sure B, must be unequal C, must be equal

3. The hour hand of the wall clock is 2.5 cm long, and the tip of this hour hand has been walking all day (B)

a . 15.7 b . 3 1.4cm c . 78.5cm。

4. The symmetry axis (c) on the right is the least.

A, circle b, square c, rectangle d, equilateral triangle

5.(b) The point that passes through the center of the circle and both ends are on the circle is called the diameter of the circle.

A, ray b, line segment c, straight line

6. The output of rapeseed this year is higher than last year 1/5, which is (c).

A, this year's rapeseed output is 102% of last year's B. Last year's rapeseed output was 20% less than this year's.

C. The rapeseed output this year is 120% D of last year, and the rapeseed output this year is 100.2% of last year.

7. A 10% discount on a certain commodity means that the price now is lower than before.

a、90% B、9% C、 1/9 D、 10%

Fifth, the operation problem. 4 points

1. Draw a circle with a diameter of 3 cm. The radius, diameter and center of a circle are represented by letters.

Sixth, graphic calculation. 9 points

1, the radius of this smiling face is 2 cm.

Given that the area of a circle is 12.56 square, find its perimeter and area. (6 points) decimeter, find the area of triangle. (3 points)

Circumference: 2× 3.14× 2 =12.56cm12.56 ÷ 3.14 ÷ 2 = 2 square decimeter area: 3.14× 2.

Seven, application questions. 30 points

1, front wheel diameter of roller1.2m, rolling 6 times per minute. How many meters can it advance per minute? 3.14×1.2× 6 = 22.608m.

There is a cow tied with an 8-meter-long rope on the wide grass. How many square meters of grass can this cow eat at most? 3. 14×8×8=200.96 m2

3. The original price of a tape recorder is 220 yuan, and the price was reduced by 20% during the 11th National Day. What's the current price? 220×( 1-20%)= 176 yuan.

4. A canteen 1 1 month burned 50 tons of coal, saving 5 tons compared with the original plan. What percentage was saved? 5÷(50+5)≈9. 1%

There is an annular flower bed with a radius of 8 meters in the garden, and a cement road with a width of 2 meters should be paved around it. What is the area of this road? 3. 14×(8+2)×(8+2)-3. 14×8×8 = 1 13.04 m2。

6. Find the area and perimeter of a semicircular pond with a diameter of 30 meters. Circumference: 3.14× 30 ÷ 2+30 = 77.1m area: 3.14× (30 ÷ 2 )× (30 ÷ 2) ÷ 2 = 353.