1. The side area of a cylinder is 125.6 square decimeters, and the height is 8 decimeters. How many square decimeters is the surface area of the cylinder? 1. The side area of a cylinder is 125.6 square decimeters, and the height is 8 decimeters. How many square decimeters is the surface area of the cylinder? 2. To make a cylindrical tin bucket without cover, the diameter of the bottom of the bucket is 4 decimeters, and the height is 5 decimeters. How many square decimeters of tin should be used at least? What is the volume of the bucket? 3. The bottom radius of a cone is 9cm, and its height is two-thirds of its diameter. What is the volume of the cone?

1. The side area of a cylinder is 125.6 square decimeters, and the height is 8 decimeters. How many square decimeters is the surface area of the cylinder? 1. The side area of a cylinder is 125.6 square decimeters, and the height is 8 decimeters. How many square decimeters is the surface area of the cylinder? 2. To make a cylindrical tin bucket without cover, the diameter of the bottom of the bucket is 4 decimeters, and the height is 5 decimeters. How many square decimeters of tin should be used at least? What is the volume of the bucket? 3. The bottom radius of a cone is 9cm, and its height is two-thirds of its diameter. What is the volume of the cone?

1. The side area of a cylinder is 125.6 square decimeters, and the height is 8 decimeters. How many square decimeters is the surface area of the cylinder?
Radius 125.6 △ 8 △ 3.14 △ 2 = 2.5 decimeters
Surface area 3.14 × 2.5 × 2.5 × 2 + 125.6
=39.25+125.6
=164.85 square decimeters
2. To make a cylindrical tin bucket without cover, the diameter of the bottom of the bucket is 4 decimeters, and the height is 5 decimeters. How many square decimeters of tin should be used at least? What is the volume of the bucket?
Iron sheet 3.14 × 4 / 2 × 4 / 2 + 3.14 × 4 × 5
=12.56+62.8
=75.36 square decimeters
Volume 3.14 × 4 / 2 × 4 / 2 × 5 = 62.8 cubic decimeter
3. The bottom radius of a cone is 9cm, and its height is two-thirds of its diameter. What is the volume of the cone?
Height 9 × 2 × 2 / 3 = 12 cm
Volume 3.14 × 9 × 9 × 12 × 1 / 3 = 1017.36 square centimeter

The perimeter of a rectangular grassland is 270 meters, the ratio of length to width is five to four

270÷2÷（5+4）＝15
Length: 15 * 5 = 75m
Width: 15 * 4 = 60m
75 * 60 = 4500m3

The third power of 8.8x10 is accurate to 10 bits. Are there two significant numbers wrong?
So why is the quartic power of 1.61x10 accurate to the hundredth

Wrong. The cubic power of 8.8x10 is accurate to 100 digits. If you want to digitize it, the following is right
Where's the thing? This number must be seen after it's translated

The speed of a train is 54 kilometers per hour. It takes 57 seconds for a train to pass through a 640 meter long tunnel

x+640=57÷60×54

As shown in the figure, △ ABC, e is the point on AC, and AE = AB, ∠ EBC = 12 ∠ BAC, the ⊙ o with ab as the diameter intersects AC at point D and EB at point F. (1) prove that BC is tangent to ⊙ o; (2) if AB = 8, sin ∠ EBC = 14, find the length of AC

(1) It is proved that AF. ∵ AB is the diameter, ∵ AFB = 90 °, ∵ AE = AB, ∵ Abe is isosceles triangle, ∵ BAF = 12 ∵ BAC, ∵ EBC = 12 ∵ BAC, ∵ BAF = ∵ EBC, ∵ Fab + ∵ FBA = ∵ EBC + ∵ FBA = 90 °, ∵ ABC = 90 °. That is, ab ⊥ BC, ∵ BC and ⊙ o are tangent

How many kilometers is four light years

Four light years is 4 * 94607304725800m
Light year, a unit of length, refers to the distance light travels in a year, that is, about 9460 billion kilometers (or 5880 billion miles). It is more formally defined as: in a Julian year (365.25 days, equivalent to 86400 seconds per day), in free space and infinitely far away from any gravitational field or magnetic field, Because the speed of light in vacuum is 299792458 meters per second (accurate), one light year is equivalent to 9460730472580 meters (accurate), or about 9.46 × 1015 meters = 9.46 beats meters
The light year is usually used to measure a great distance, such as the distance between the solar system and another star. The light year is not a unit of time. In astronomy, the second gap is a very common unit, which is equal to 3.26 light years
A light year is also equivalent to 63240 astronomical units
It takes about eight minutes for light to reach the earth from the sun
It is known that the nearest star to the solar system is Sagittarius, which is 4.22 light years apart
Our galaxy, the Milky way, is about 100000 light-years in diameter
If there is a spaceship with near light speed from one end of the galaxy to the other, it will take more than 100000 years. But this is only for the static observer, the journey experienced by the crew is only a few minutes. This is due to the time expansion of the moving clock in special relativity
The diameter of the visible universe is about 15 billion light years

Teach Laozi a math problem
The distance between the two stations is 475km. A and B cars leave from the two stations at the same time. A car's speed is 50km, and the speed of the car is 45km. How many hours will the two cars meet

Let (50 + 45) x = 475 95x = 475 x = 5

In trapezoidal ABCD, AD / / BC, ∠ B = 40 ° and ∠ C = 50 °, m.n is ad, BC midpoint, BC > ad respectively, and Mn = half (BC-AD)

In trapezoidal ABCD, ad is parallel to BC, angle B = 40 degrees, angle c = 50 degrees, Mn is the midpoint of BC ad respectively, and Mn = 1 / 2 (BC-AD) is proved
1:
Extend Ba CD to intersect p
Angle B + angle c = 90 degrees
Right triangle PBC pad
M n is the middle point, PM = 0.5bc, PN = 0.5ad
MN=PM-PN=0.5（BC-AD）
2:
Make AE / CD and hand it to BC in e
Then: AECD is a parallelogram, CE = ad
And: ∠ AEB = ∠ C = 50
∠BAE=180-(∠B+∠AEB)=180-(40+50)=180-90=90
Let f be the midpoint of AE, AF = be / 2 = (bo-ce) / 2 = (BC-AD) / 2
MF=BM-BF=BC/2-BE/2=BC/2-(BC-CE)/2=CE/2=AD/2
AN=AD/2
So, an / / FM, an = FM
Therefore, afmn is a parallelogram
AF=MN
So, Mn = 1 / 2 (BC-AD)

If the mass of a piece of metal is 8.9 times the cubic kg of 10, and its volume is 3M & sup3;, then the density of the metal is (). If it is intercepted in general, then its mass is (). Its volume is (). Its density is ()
The density of copper is 8.9 times 10 to the third power kg___________

966g / cm3, 4450kg, 1.5m3

The starting price of a taxi in a city is 7 yuan [the distance is within 3000 meters] for a distance of more than 3000 meters, 1.2 yuan per kilometer [less than 1 kilometer is calculated as 1 kilometer]
Xiaohua takes a taxi from home to the gymnasium. The total fare is 21.4 yuan. How many kilometers is the journey from Xiaohua's home to the gymnasium

Pro, the longest distance from Xiaohua's home to the gymnasium is about 9 kilometers;
Details are as follows:
21.4-7 = 14.4 yuan
14.4 / 1.2 = 12 km
12-3 = 9 km (minus starting 3 km)
The above, please know, there is unknown, please ask again!