Two math problems 6th grade about the circle Heroes please enter Hurry Rush Hurry Rush

The unit of circumference of that semicircle is meters:m.

First, calculate the radius r of the circle, let the radius of the circle be x(m), and the diameter of the circle be 2x(m).

Equation: 2*

The solution is x=5 the area of the semicircle: 5 squared and 2=square meters.

Question 2: Actually, the diameter of this circle is the length of the sides of the square.

Side length a = root number 10 cm

The radius of the circle is one-half of the root number 10

The area of the circle: the square of the root number 10 (both 10) = square centimeters.

1.Let the radius of this semicircle be a

Then the perimeter c = diameter + arc length of the semicircle = 2a + 1 2 * 2a = 2a + a = (2+ )a

So the radius is m

So the area is 5*5* =25 = square meters.

r 2 is the square of r.

2.Let the radius be r, then the side length is 2r, so 2r*2r=10r 2=

So the area is r 2= square centimeters.

Circumference = circumference 2 + diameter = d 2 + d = (1 + 2) d take =

Rule. Circumference = (1 + 2) d = (1 + m).

then d = 10 meters.

Area = area of the circle 2=( d*d 4) 2=square meter) The diameter of the maximum circumscribed circle of the square is equal to the length of the sides of the square.

Then the diameter of the circle d = 10 (cm).

then the area of the circle = d*d 4 = square centimeters).

1) Set the diameter of the semicircle to x

x = 2570 414 2570 207 times.

2) 5 times 5 times.

According to the formula s=r

There is another question to know.

The radius of the great circle is 2 times the radius of the small circle, then the area of the great circle is 4 times the area of the small circle, and the area of the large circle is 12 square meters more than the area of the small circle.

It can be seen that the area of a small circle is 12 divided by 3 equal to 4 square meters.

Set the radius of the small circle.

x is the radius of the great circle.

2x(2x) squared - (x)squared =12

3x squared = 12

x square = 4

So the area of the small circle is equal to 4

This is a problem of calculating the circumference and area of a circle.

1. The distance traveled by the tip of the minute hand is the circumference of the clock From the question, it can be seen that the radius is 30cm c= The area swept by the minute hand is the area of this circle (because the hour hand exactly turns on the clock surface) s=

2 The diameter is 8cm, the radius is 4cm, and the area is the pi multiplied by the radius squared.

3 Calculate the area swept by each range, which is closest to 314 square meters (the answer is 10cm).

4 This is the problem of circumference, you first have to calculate how many meters the wheel turns, and then multiply it by 50, and then you will solve it.

I hope you understand what I'm saying.

1: The minute hand of a clock is 30 cm long, and after 1 hour, how many centimeters does the tip of the minute hand travel? How big is the area swept by the minute hand?

The length of the sweep and the perimeter).

2: There is a circular pool with a diameter of 8m, how big is the area of this pool?

3: There is a circular lawn with an area of 314 square meters, and it is ready to be equipped with automatic rotary sprinkler irrigation. There are three types of devices with a range of 20m, 15m, and 10m, which do you think is the right choice? Where is it installed on the lawn?

314 100 = 10 10 So choose a 10m device.

4: A bicycle, its outer diameter of the wheel is 80cm, if the wheel turns an average of 50 times per minute, then how many meters can the bicycle travel per minute?

80cm = meters.

The hour is a circle, so it means to calculate the circumference of the circle, the circumference of the circle: 2 r=2*; The area swept is the area of the circle: s = r 2 = square centimeters.

m3According to the area of the circle s= r 2,314 = we get r = 10m. A 10m installation is installed in the center.

4.Circumference c=2 r=2* 50 laps is 50*

1. The minute hand travels a full circle in one hour, so the distance traveled by the tip of the minute hand is. The area swept is a square centimeter.

2. The floor area of the pool is square meters.

3. Choose a 10m device and install it in the center of the lawn.

4. The bicycle walks meters per minute hand.

1.The minute hand is circled in one hour, so the distance is the circumference = 2 r =, and the area swept is the area of the circle = r = 2826 square centimeters.

2.The diameter is 8m, the radius is 4m, and the area is r = square meter 3The area of the circle is 314 square meters, the area is equal to r, it can be calculated that the radius is 10m, the device with a range of 10m is selected, installed in the center of the circle.

4.Each revolution is the circumference, the circumference is 2 r=2*, and 50 revolutions per minute, then it is 50*circumference=12560cm=

The inner and outer sides are similar, the corresponding side length is proportional, the outer perimeter: the inner perimeter = r: r = 44:40 = 11 10, the outer perimeter = the internal perimeter * (11 10) = 400 * (11 10) = 440 meters, 440-400 = 40 meters, the starting point should be 40 meters apart, so that the run is the same length.

HelloThat is true... You draw two runways.

The one inside is 400m. Pick a random starting point on that runway inside. The inner and outer sides are similar, the corresponding side length is proportional, and the outer perimeter is proportional

Internal perimeter = r: r = 44:40 = 11 10, outer perimeter = internal perimeter * (11 10) = 400 * (11 10) = 440 meters, 440-400 = 40 meters, the starting point should be 40 meters apart, so that the run is the same length That's almost it The runway is not a circle、、、 that enthusiastic netizen.

The length of the corresponding side is proportional, and the outer perimeter: the inner perimeter = r:r=44:

40 = 11 10 outer perimeter = internal perimeter * (11 10) = 400 * (11 10) = 440 meters, 440-400 = 40 meters, the starting point should be 40 meters apart, so that the run is the same length.

2*m≠400m, the runway is not a circle.

The runway is similar to an oval, it is two straight lines plus two and a half circles, the length of the straight line is equal, and the length of the outer ring and the inner ring of the two and a half circles are 2 meters apart.

The starting point of the two should be meters apart, and Xiao Gang is in front of Xiao Ming. In this way, the distance is the same as long

Analysis: The runway is generally a rectangle with 2 semicircles on both sides, so the perimeter should be calculated with the length of 2 sides of the rectangle plus the arc length of 2 semicircles. Because the straight line is partially offset when the inner and outer circumference are subtracted, the circumference of the outer runway is 2* *44-2* *40=8 meters more than the inner side, and they race 400 meters without more than one lap, so Xiao Gang can start at the front 8 meters.

1. 1 The diameter of a wheel is 50cm, and the wheel rotates for one time, about forward ( m.

2 When the distance between the feet of the compass is 5 cm, draw the circumference of the circle as ( cm.

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

4 The outer diameter of a ring is 10 cm, the inner circle is 8 cm, and its area is ( cm2.

5.Bend a decimeter of wire into a circular ring (excluding the interface), the diameter of the ring is ( decimeter, the area is ( square decimeter.

6 The formula for calculating the circumference of a circle is: ( or (

The formula for calculating the area of a circle is: (

2. Judgment is true or false.

1. The diameter is always longer than the radius. （

2. The center of the circle determines the position of the circle, and the radius determines the size of the circle.

3. The area of a circle is equal to the area of a square, and their circumferences are also equal. (4. The circumference of a semicircle is half of the circumference of this circle.)

5. Of all the line segments with both ends on the circle, the diameter is the longest one.

3. Choice. 1. In the following figures, the axis of symmetry is the most (

a, square b, circle c, isosceles triangle 2, the minute hand of a clock is 10 cm long, from 2 o'clock to 4 o'clock, the minute hand has passed ( cm.

a、 b、 c、314

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

a、 b、 c、314

4. Pi (

a, greater than b, equal to c, less than.

5. A semicircle, the radius is r, and its circumference is (

1.A circle is a circle with a radius of r = root number 2 + 1) and a circumference of l = 2 r

Bundle 4 turns is the length of 8 r 2

Fill in the blanks times.

157/100

The approximate rate is 22 7, the density rate is 355, the Nian Pai 113, and the more dense rate is 52163 16604

Location. It should be used for 678247 minutes.

7. Draw the largest circle within a square, and the area of this circle is the area of the square (