The length of a cylindrical wood is 4dm, and the bottom radius is 10cm. After cutting it into three sections, the surface area increases by () cm2? A.942 b.1256 c.1884

The length of a cylindrical wood is 4dm, and the bottom radius is 10cm. After cutting it into three sections, the surface area increases by () cm2? A.942 b.1256 c.1884

After cutting into three sections, the surface area increased by (3-1) × 2 = 4 bottom surfaces
Therefore, the surface area increases
14 × 10 & # 178; × 4 = 1256 square centimeter
Selected from: b.1256

The length of a cylindrical wood is 4cm, and its bottom radius is 10cm

1256 square centimeters

(the formula is OK)
1. There are 48 people in a class. Everyone can play chess (chess or go). The number of people who can play chess is twice as many as those who can play go and admit defeat. There are three less people. There are at most nine people in both classes, but not less than five people. How many people can play go?
2. In 2007, a certain department of a university plans to enroll 120 students, of which the number of students enrolled in the province is less than two-thirds of those enrolled outside the province, but more than one-third of those enrolled outside the province. How many students will the department enroll in the province and outside the province?
3. Give a pile of apples to several children. If each of them has three apples, there will be eight left. If each of them has five apples, the last one will get less than three apples. How many children and how many apples are there?

1 is 19
Let X be the number of chess players and y be the number of go players
x+y-5>=48
x+y-9

As shown in the picture, there are two squares of different sizes, with a difference of 95 square centimeters in area

Let the side length of a small square be a centimeter. According to the meaning of the question, we can get the equation: 5A + 5A + 5 × 5 = 95 & nbsp; & nbsp; & nbsp; 10A + 25 = 95 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 10A = 70 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; A = 77 × 7 = 49 (square centimeter) 49 + 95 = 144 (square centimeter) answer: the area of a small square is 49 square centimeter, and that of a large square is 144 square centimeter

A celestial body, like the earth, which does not emit light on its own and revolves around the sun, is called the?

Planets
The sun, which glows and heats itself, is called a star, while the planet is called a satellite. Generally speaking, a star is bigger than a planet, and a planet is bigger than a satellite

In the second year of science, there are 10 questions about the calculation of water pressure and density,

1. A square metal block with variable side length of 0.1M, weighing 100N, is placed in the center of a horizontal desktop with an area of 1m2. What is the pressure of the metal block on the desktop?
2. There is a cylindrical container and a cylindrical metal block with enough length, its cross-sectional area s: s column = 3:1, the container is filled with water, and the metal block is suspended under a thin line. Now put the metal block into the water slowly. Question 1: if the cylindrical metal block is immersed in the water for 15 cm, how much pressure is exerted on the bottom of the container
3. When the thumbtack is pressed by hand, the pressure and pressure of the hand on the thumbtack cap are F1 and P1 respectively; the pressure and pressure of the thumbtack tip on the wall are F2 and P2 respectively, then ()
A、F1＞F2； B、F1＜F2； C、P1＞P2； D、P1＜P2.
4. Three solid cylinders with the same height and different thickness are made of iron and placed vertically on the horizontal table top. As shown in the figure, the pressure on the table top is PA, Pb and PC respectively, then ()
A. PA ＜ Pb ＜ PC; B, PA ＞ Pb ＞ PC; C, PA = Pb = PC; D, unable to judge
5 as shown in the figure, there is water in the sealing cone. If it is inverted, then ()
A. The pressure of water on the bottom of the container decreases and the pressure increases;
B. The pressure of water on the bottom of the container decreases and the pressure decreases;
C. When the pressure of water on the bottom of the container increases, the pressure increases;
D. The pressure of water on the bottom of the container increases and the pressure decreases
The height of the dam of a hydropower station is 105 meters, the water depth in the dam is 75 meters, and the pressure of water on the dam is ()
A. 5 × 104 Pa; B, 6. 86 × 105 Pa; B, 6;
C. 5 × 105 Pa; D, 1.05 × 106 PA
The maximum pressure that a submersible can bear is 1 × 107 PA, then the maximum concentration of the submersible in the water can reach ()
A. 100 meters; B, 1 km; C, 10000 meters; D, 100000 meters
When a wooden box with a bottom area of S is placed in the center of the table top of a square table with an area of 2S, the pressure of the wooden box on the table top is p. when a small square stool with an area of S / 2 is placed in the center of the wooden box, the pressure of the wooden box on the table top is ()
A、P/2； B、P； C、2P； D、4P.
8. A kind of red brick for building, its density is 1500 kg / M & sup 3;, and the maximum pressure that each red brick can bear is 750000 Pa. if this kind of red brick is used to build a building whose height is 3.3 m, how many floors can be repaired at most? (excluding the thickness of mortar)
9. There is a 76cm high mercury column in a 1m long vertical glass tube. How much pressure does the mercury column produce on the bottom of the tube? How high is the water column to produce such a large pressure?
The total volume of sulfuric acid is 500 ml. the container is placed on a horizontal table with an area of 1000 cm. The thickness and weight of the container are not considered
1. The pressure of sulfuric acid on tabletop;
2. The pressure of sulfuric acid on the tabletop;
3. The pressure of sulfuric acid on the bottom of the container;
It is known that the density of ice is 0.9 * 10 ^ 3. The volume ratio of ice and water with the same mass is v ice: V water=_______ For the same volume of ice and water, the mass ratio m ice: m water=_______ .

A circular boiler, the circumference of the bottom circle is 1.57 meters. How many square meters is its bottom area? (two decimal places reserved)

1.57 △ 3.14 △ 2, = 0.5 △ 2, = 0.25 (m), 3.14 × 0.252, = 3.14 × 0.0625, ≈ 0.20 (M2); a: its bottom area is 0.20 m2

The simple calculation is 7 / 15 × 1 / 5 + 4 / 5 △ 15 / 7

7 / 15 × 1 / 5 + 4 / 5 ÷ 15 / 7
= 7 / 15 × 1 / 5 + 4 / 5 × 7 / 15
= （7 / 15）（1 / 5 + 4 / 5）
= 7 / 15 × 1
= 7 / 15

Simplification: (SiNx * cosx) / [(cosx) ^ 2 - (SiNx) ^ 2] - TaNx / [1 - (TaNx) ^ 2]

Equal to 0.: (SiNx * cosx) / [(cosx) ^ 2 - (SiNx) ^ 2] - TaNx / [1 - (TaNx) ^ 2]
=1/2(sin2x/cos2x-1/2tan2x=1/2tan2x-1/2tan2x=0

For square and circle with equal perimeter, the ratio of side length to radius is______ ：______ The area ratio is______ ：______ ．

The ratio of side length to radius is: C4 ／ C2 π = C4 × 2 π C = π 2, the ratio of area is: (C4) 2 ／ [π × (C2 π) 2] = c216 ／ [π × C24 π 2] = c216 ／ C24 π = c216 × 4 π C2 = π 4, answer: the ratio of side length to radius is π: 2, the ratio of area is π: 4