Of the 22%, one fifth, 0.2 1, 0.202 and two-ninth (in descending order), and 22% (0.22) > 0.202 & gt 0.21> One fifth (0.2)
Interest = (principal * interest rate * time)
True or false:
After subtracting 20% from a rope, connect the remaining 20% with the same length.
Wrong. You subtract 20% from the original length and add the remaining 20%. And the remaining 20% is not equal to 20% of the original length.
Xiaohong's mother's monthly salary 1800 yuan. After deducting 1.600 yuan from her monthly salary, she will pay the balance of 5%, and Xiaohong's mother will turn it over to 40 yuan every month.
The wrong balance is 200. And 5% is 50% with decimal point. That is 200, 100,1half of 0 yuan. In fact, 1800 is not a high income. How can 40 yuan pay taxes?
Add 1 g salt into 10 g water, and the salt accounts for 10% of the brine.
The wrong brine is salt and water. 1 divided by 1 1 is not equal to 10%. The primary school hesitated because of the entanglement of the paper, but I still chose the right one. Thank you ~ ~ ~ Miss ~ ~
Cylinders and cones with equal bottoms and equal heights. The volume of a cylinder is two thirds larger than that of a cone.
Volume of cylinder = bottom area * height; Cone volume = 1/3* bottom area * height.
Put a cubic decimeter object on the table, and its area on the table is 1 square decimeter.
Wrong this object is not a cube, a cube (area = side length * side length ×6, and one surface area = side length * side length; Volume = side length * side length * side length) is correct?
The side development diagrams of cylinders are all rectangular.
I'm not sure. Look at the teacher's textbook. A parallelogram with four corners at right angles is called a rectangle. Considering that you are in elementary school mathematics. I remember that squares and rectangles were separated in primary school. After junior high school, rectangles are equivalent to rectangles, and squares are special rectangles, so squares are included in rectangles, and squares are also rectangles.
The volumes of cubes, cuboids and cylinders can all be equal to the bottom area multiplied by the height.
Cubes, cuboids and cylinders are all cylinders. If you have studied cross-sections, you will know that the shape and size of each horizontal cross-section are the same, otherwise the top view can't be just a single figure without dotted lines or something. Therefore, we can regard it as an object piled up by countless figures with the same shape and equal size.
To know how much water a cylindrical cup can hold, you must know the surface of the cup.
Wrong. Just think about it and you will know that it is volume.
Find the volume (unit decimeter)
Height 7 diameter 6 cone
V =1/3sh =1/3 (π * r * r) H. Mastery is to multiply the square of one-third πr by h pupils. If you are not so proficient, you can use Sh. In fact, there are two steps, and the two formulas are essentially the same. R= 1/2d= 1/2*6=3 (decimeter); S=3. 14*3*3=28.26 (square decimeter); V =1/3 * sh =1/3 * 28.26 * 7 = 65.94 (cubic decimeter)
A cylinder with a diameter of 4 and a length of 16.
V = SH = (π * r * r) H. It is familiar that πr times the square of hr = 1/2d= 1/2*4=2 (decimeter); S=3. 14*2*2= 12.56 (square decimeter); V = SH =12.56 *16 = 200.96 (cubic decimeter)
Calculate and solve equations (with process quantities)
Seven thirds X 12% divided by 2 1/5.
Solution: 7/3 *12% ÷ 21/5 = 7/3 * 25 * 5/21=1/5.
28.8.-640%-2.8- 23/5
For the sake of simplicity, we magically find that among various exchange association rules, 2 1/5=4 and 3/5 (with scores). 3/5 is a finite decimal 0.6. So the first step is to convert 2 1/5 into decimals.
Solution: 28.8-640%-2.8-23/5 = (28.8-2.8)-6.4-4 and 3/5 = 26-6.4-4-0.6 = (26-4)-(6.4+0.6) = 22-7 =
In fact, there are several steps that can be omitted, and they are written for you to see clearly.
2x+30%= 2 1/2
Why choose all decimals? Because 30% can be converted to 3/ 10 at most. The denominator on the right is 2, which is also a variety of general points; When 30% is converted into decimal, it is a finite decimal 0.3.
Solution:
2x+30%=2 1/2
2x=2 1/2-0.3
X = (10.5-0.3)/2 ... (Left and right sides are divided by 2 at the same time)
x=5. 1
50%+ two thirds x= 17/ 15
Solution:
50%+2/3*X= 17/ 15
1/2+2/3 * x = 1+2/ 15
2/3*x= 1/2+2/ 15
20x = 15+4 ... The left and right sides are multiplied by the least common multiple of 30.
x= 19/20
1.5x-20%= 1
Solution:
1.5x-20%= 1
1.5X= 1+20%
1.5x= 1.2
x=6/5*2/3
x=4/5
x=0.8
Application problems (and processes)
1. A conical sand pile with a height of 3m, a bottom circumference of 3m1.4m and a sand weight of1.5t per cubic meter. How many tons does this pile of sand weigh?
Solution: The volume of this pile of sand:
C = 2π r = c/2π = 5 (m)
S=πr*r= 1/2Cr
v = 1/3SH = 1/3 * 1/2 * * 3 1.4 * 5 * 3 = 78.5(m3)。
Weight of this pile of sand: 78.5 *1.5 =117.75 (ton)
If you don't know how to refer to the above process, there are not too many steps.
2. How many pieces of iron sheets are needed to make 100 cylindrical chimneys, each section is 5 decimeters, and the bottom diameter is 10 cm?
Solution: each cylinder needs iron sheet: (the chimney has no bottom and no top, which is equal to the rectangular area of the side)
S = ab = π d * b = 3.14 *10 * 50 =1570 (square centimeter)
Therefore, the iron sheet required for 100 section:157 *100/100 =1570 (square decimeter).
3. A cylindrical beverage can needs wrapping paper (diameter 10cm, height 15cm).
1 m2 How many sheets of such wrapping paper can you make at most?
What is the volume of this beverage can?
Solution: common sense beverage cans are only attached around:
A beverage can needs a sticker: s = ab = π d * b = 3.14 *10 *15 = 471(square centimeter).
1 m2 Number of sheets that can be made:10000 ÷ 471= 21.23 = 21(sheets) ... Note that the worksheet is an integer.
V = SH = 3.14 * 5 *15 =1177.5 (cubic centimeter)