1、 A cylindrical iron bucket, measuring from the inside the bucket depth of 5 decimeters, the bottom diameter is 4 decimeters, how many kilograms of water can this bucket hold? 2、 How many cubic meters of rice can a cylindrical grain bin hold? 3、 The diameter of the bottom surface of a cylindrical wood is 12 cm. What is the volume of this wood cubic cm?

1、 A cylindrical iron bucket, measuring from the inside the bucket depth of 5 decimeters, the bottom diameter is 4 decimeters, how many kilograms of water can this bucket hold? 2、 How many cubic meters of rice can a cylindrical grain bin hold? 3、 The diameter of the bottom surface of a cylindrical wood is 12 cm. What is the volume of this wood cubic cm?

Area formula of circle: square of radius × circumference, volume formula of cylinder: bottom area × height
First question: height = 0.5m radius = 0.2m water density: 1000 kg / m3
It's easy to know the answer: 3.14 * 0.2 * 0.2 * 0.5 * 1000 = 62.8kg
In addition: circumference = 3.14 * d = 3.14 * 2R, you can calculate the other two problems

1. On a straight road, a rides at a speed of 15 m / s, and B rides at a speed of 5 m / s in front of A. when a sees B in front of him, he immediately stops pedaling and decelerates naturally. After 10 s, a just catches up with B and does not collide. If a and B are 20 m apart, how long does a slide (accurate to 0.1 s)
2. In order to expand a swimming pool with a length of 100 meters and a width of 60 meters into a large water playground with a perimeter of 600 meters, if the length of the swimming pool is increased by X meters, then when x is equal to what, the area of the water playground is equal to 20000 square meters? Can the area of the water playground be equal to 23000 square meters? If so, calculate the value of X; if not, please explain the reason
3. An acrobatic troupe uses a 68m long curtain to encircle the city, a rectangular temporary site with an area of 300 square meters, and leaves 2m as the entrance and exit, then the length and width of the rectangular site are?
4. It is known that the univariate quadratic equation x & sup2; + X + a = 0 and X & sup2; + ax + 1 = 0 have a common real root and the value of ball a

Let a's acceleration of deceleration be a, then a = (15-5) / 10 = 1 m / S ^ 2. Let a and B be separated by L meters, then a can see B, then there is a formula L + 5 * 10 = 15 * 10-0.5 * a * 10 ^ 2

What are the answers to some math problems
The first order equation of one variable is used to solve the equation
1. China's GDP in 2001 was 9593 billion yuan, an increase of 7.3% over 2000. How many billion yuan was China's GDP in 2000?
2. There are 200 chickens and rabbits in a farm, which have 536 legs. How many chickens and rabbits are there respectively? Can the 200 chickens and rabbits have 525 legs? If possible, how many chickens and rabbits are there respectively? If not, why not
3. If the ratio of length to width of a rectangle is 5:3 and the ratio of length to width is 12, then the length and width of the rectangle are ()
4. Please read the following poem: "there are a group of crows living in the tree. The crow tree is unknown. There are three crows living in a tree. Five of them have no place to go. There are five crows living in a tree. If you have a tree idle, please count carefully. The crows mentioned in the poem bureau are () crows and the trees are () crows
5. Class 1 of Grade 7 bought 25 prizes with 80 yuan. Each prize is a ballpoint pen and an automatic pen. If it is known that each ballpoint pen is 2.5 yuan, the automatic pen is () yuan
6. A student finished reading a book in three days. On the first day, he read 30 pages more than on the second day and 40 pages less than on the third day. On the third day, he read 2 / 5 of the book, so the book has () pages in total
7. The surface of a football is surrounded by black Pentagon and white hexagon. It is known that black leather is 3 / 5 of white leather. There are 32 pieces of leather on the surface of a football, and there are () pieces of black leather and () pieces of white leather
8. "Home appliances to the countryside" farmers get substantial benefits. Villager Xiao Zheng bought a double door refrigerator, after deducting 13% of the government financial subsidies, and then subtracted 100 yuan from the "home appliances to the countryside" consumption volume presented by the shopping mall. In fact, it only cost 1726.13 yuan. The selling price of the refrigerator is x yuan. The equation can be solved and x =
2. I've learned to pull v

18940.354 billion yuan
There are 132 chickens and 68 rabbits
200 chickens and rabbits can't be 525, because rabbits can't have only two feet
3. 30 in length and 18 in width
4. There are 20 crows and 5 trees
5.0.7 yuan
6. 550 pages
7. Black 8 is 12 pieces, white is 20 pieces
8. 2099 yuan