2. A cylindrical glass cylindrical container with a volume of 628 liters. If a quarter of water is injected into the container, and the water is still 30 cm away from the cylinder mouth, the bottom area of the container is found.
3. A cube with a length of 40 cm has a round hole with a diameter of 4 cm above and below, and the hole depth is 10 cm.
First question: What is the surface area of this three-dimensional figure?
The second question: What is the volume of this three-dimensional figure?
Answer:
1
The bottom area of the cylinder is 3. 14 square centimeter.
According to the area formula of the circle, the radius of the circle can be calculated = 1 cm.
Circumference =2*3. 14=6.28.
Transverse area = perimeter x height
Then the height after adding 2 cm =43.96/6.28=7 cm.
Original height = 7-2 = 5cm.
Volume = bottom area x height =3. 14*5= 15.7 cubic centimeters.
2
628000*(3/4) divided by 0.3 equals 15700 (square centimeter).
three
(1) surface area The surface area is the area of a cube minus the areas of two circles:
40*40*6=9600 (square centimeter)
4 * 3.14 *10 * 2 = 251.2 (square centimeter)
9600+251.2 = 9851.2 (square centimeter)
(2) The volume is the volume of the cube minus the volume of the cylinder:
Square of 40*40*40-2*π*2 * 10 = 9600-40 π = 63748.8 (cubic centimeter
Basic knowledge of algebra
Fill in the blanks
Use letters to indicate the following quantities.
1. The library has X books and bought 240. There are () books in the library now.
2. Each book is RMB X, and Xiaoming bought 6 books, and the amount payable is RMB ().
The weight of apple is one kilogram, and the weight of pear is three times that of apple. Then, 3a stands for ().
4, A minus B, the difference is 8, A is A and B is ().
5. The circumference of a square with a side length of b cm is () cm and the area is () cm.
6. The train travels 78.5 kilometers per hour and () kilometers per hour.
7. Say the meaning of each formula.
(1) Students in Class One do a math problem A every day, denoted by 7a.
(2) Grade four students subscribe to China Youth Daily 120, which is x more than grade five, 120-x indicates. China Youth Daily costs one yuan each, 120a, (120-x) a) a.
(3) The side length of a square is one centimeter, denoted by 4a and denoted by a2.
(4) Teacher Zhang bought three volleyballs, each at X yuan, and paid the salesman 245 yuan, 245 -3x.
8、0.9∶0.6=9∶( )
9. If y=5x, then x and y are proportional to ().
10 1/2:3/4 The simplest integer ratio is ().