![](data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 72 71" width="72"></svg>)
The outer circumference of a ring is 25.12 cm, and the inner circumference is 18.84 cm
Outer circle radius: 25.12 / (3.14 * 2) = 4
Inner circle radius: 18.84 / (3.14 * 2) = 3
Area of ring: 3.14 * (4 * 4-3 * 3) = 21.98
The width of a ring is 2 cm, the sum of the circumference of the outer circle and the inner circle is 25.12 cm, and the area of the ring is 2 cm
If the radius of the inner circle is x cm, the radius of the outer circle is (x + 2) cm
2×3.14×（x+x+2）=25.12
2x+2=4
x=1
x+2=3
Ring area = 3.14 × (3 & # 178; - 1 & # 178;) = 25.12 square centimeter
If the diameter of the inner circle of a ring is 6cm and the width of the ring is 2cm, then the diameter of the outer circle is 5cm__ Cm, circumference is__ centimeter
First find the diameter of the outer circle: 6 + 2 + 2 = 10 (CM)
Circumference of outer circle: 10 π = 10x3.14 = 31.4 (CM)
How many meters away is a 70 meter man standing three meters in front of a 1-meter-high vertical plane mirror?
Known: object distance u = 3M,
According to the characteristics of planar mirror imaging, the distance between the image and the mirror is equal to the distance between the object and the mirror,
Then the distance between the image and the object is: U + V = 3M + 3M = 6m
Xiao Ming's height is h. he wants to see his whole body through a plane mirror. How high does the mirror have to be to meet Xiao Ming's requirement
And how should this mirror be placed?
H / 2 in fact, the answer ignores the distance from the eye to the top of the head
Xiao Liu is 1.7 meters tall, standing 1.5 meters in front of a plane mirror placed vertically. What is his height______ If he gets closer to the flat mirror, the distance between his image and the flat mirror will be shorter______ The height of the image will______ (select "increase", "decrease" or "unchanged")
(1) Because the size of the image is the same as that of the object, the height of the person is 1.7m, so the height of his image is also 1.7m; (2) because the distance between the image and the object and the mirror is equal, if he approaches the plane mirror, the distance between his image and the plane mirror will also decrease, but the height of the image remains unchanged
A classmate is 1.5 meters tall, standing 3 meters in front of the plane mirror. How many meters is the distance between her image and the mirror, and how many meters is the image height
A classmate is 1.5 meters tall, standing 3 meters in front of the plane mirror. The distance between her image and the mirror is 3 meters, and the image height is 1.5 meters
The height of a classmate is 1.70m. Standing in front of a 1.2m high plane mirror and 1.5m away from the plane mirror, his image height is 1.70m___ m?
1.70m
A 6-meter-old man stands three meters in front of a 1-meter-high vertical plane mirror. How high is his image in the mirror
The image is also 1.6 meters high. According to the law of plane mirror imaging, the object and image are equal in size
It has nothing to do with the distance between you and the plane mirror. It seems that the farther away you are from the plane mirror, the smaller you want to be. But in fact, it's not like this. The size of the image (including height) remains the same. It seems that the smaller you are because of the angle of view
A person's height is 1.8 meters. If you want to see your whole body image in a plane mirror, how many meters of wearing glasses should you buy at least
As shown in the figure, ad is a person, a is the head, D is the foot, B is the eye, Fe is the mirror, and Fe ∥ ad, make FB ⊥ ad in B, intercept Ag = 2Ab, C is the midpoint of Gd, make EC ⊥ ad in C, EF is the mirror
∵AG＝2AB,BF⊥AG,GD＝2GC,EC⊥GD
The AG is divided vertically by FB and the GD is divided vertically by EC
And ∵ ad ∥ EF,
∴2FE＝AD
And ∵ ad = 1.8m
∴FE＝1.8×0.5＝0.9m
A: the mirror should be at least 0.9m
RELATED INFORMATIONS
- 1. The perimeter of a round vegetable field is 18.84. If the perimeter is widened by 3 meters, how many square meters will the area increase compared with the original one?
- 2. 1. There is a circular vegetable field with a perimeter of 1884 meters, which is widened by 4 meters around. What is the perimeter of this vegetable field now? 2. The diameter of a circular flower bed is 18 meters. A circular path with a width of 1 meter is paved around the flower bed. What is the floor area of this path
- 3. Arc calculation: chord length 15.7m, chord height 15m, radius 9.55, arc length? Chord length 0.6m, chord height 0.6m, radius 0.38M, arc length? Help me. I'm wrong
- 4. The chord length is 4.85M, the chord height is 0.7m, what is the arc length and how to calculate it?
- 5. Given chord length 2.2M, chord height 0.5m, radius 1.47M, calculate arc length
- 6. Known arc length 785, diameter 750, angle 60 degrees, find chord length Half TCA 750cm
- 7. It is known that the chord length of a circle is 3.8 meters, and the corresponding arc length is 5.5 meters
- 8. Given the radius and arc length, how to draw the arc with CAD
- 9. Calculate the arc length when the radius is 11 meters and the chord length is 0.5 meters
- 10. If the side area of a cylinder is 50.24 square centimeter and the height is equal to the bottom radius, what is the surface area?
- 11. A circular paperboard, 25.12 cm circumference, 1 cm radius, circular paperboard area
- 12. How to calculate the diameter, radius and circumference with circle area
- 13. For a circle 4 cm in diameter, find the perimeter and area
- 14. The diameter of the round table top is 1.2 meters. The area of the table top is () the perimeter of the round object is 18.84 cm, and its area is ()
- 15. The circumference of the outer ring is 25.12cm, and the circumference of the inner circle is 18.84cm
- 16. For a ring, the circumference of the inner circle is 31.4cm and the circumference of the outer circle is 94.2cm. What is the area of the ring?
- 17. As shown in the picture, a ladder is 25 meters long, leaning against a wall, and the bottom B of the ladder is 7 meters away from the wall 【1】 How high is the top of the ladder from the ground? [2] if the top of the ladder falls 4 meters, how many meters does the bottom of the ladder move horizontally?
- 18. A ladder is 25m long, leaning against a wall. The low end of the ladder is 7m away from the wall. How high is the top of the ladder from the ground?
- 19. A 10 meter long ladder leans against the wall. The vertical distance between the top of the ladder and the ground is 8 meters. After the top of the ladder slides 2 meters, will the bottom slide 2 meters horizontally? Try to explain the reason
- 20. As shown in the figure, in a room, there is a ladder leaning against the wall. The vertical distance Ma between the top of the ladder and the ground is a meter. At this time, the gradient angle of the ladder is 75 degrees. If the bottom of the ladder does not move and the top of the ladder is leaning against the opposite wall, the vertical distance NB between the top of the ladder and the ground is B meter and the gradient angle of the ladder is 45 degrees, then the width ab of the room is () A. A + B2 m B. a − B2 m C. B M D. a m