How can a 2m long wood with a diameter of 20cm be counted as a cube? For example, the cubic formula of wood processing plant: Diameter 10cm = 0.019, how did this 0.019 come from? Diameter 12cm = 0.027? Diameter 14cm = 0.036? Diameter: 16cm = 0.047? Diameter 18cm = 0.059? Diameter 20cm = 0.072? Diameter 22cm = 0.086? Diameter 24cm = 0.102? Diameter 26cm = 0.12? All the above are two meters in length. What's the reason for his formula? If it's three meters or 3.5 meters in length, how should it be calculated?

Area of circle = π R ^ 2
Area X length = volume
You provide the formula is the volume of 2 meters long cylinder wood, the unit is cubic meter, and add 0.4 ~ 0.5 surplus
Other lengths can also be calculated according to the above formula. It can also be multiplied by the ratio according to the existing formula. For example, if the length is three meters, it can be multiplied by 1.5

Saw a 3-meter-long cuboid wood into four sections, the surface area increased by 96 square centimeters, the original volume of this wood is______ Cubic decimeter

3 meters = 30 decimeters, 96 square centimeters = 0.96 square decimeters, 0.96 △ 6 × 30, = 0.16 × 30, = 4.8 (cubic decimeters); answer: the original volume of this wood is 4.8 cubic decimeters. So the answer is: 4.8

Saw a 1.5-meter-long cuboid wood into four sections, and the surface area increased by 96 square centimeters. How many cubic decimeters was the original volume of this wood?

Saw the wood into 4 sections and added 6 sides:
(4-1) × 2 = 6
What is the area of each cross section
96 △ 6 = 16 (cm2)
16 square centimeter = 0.16 square decimeter
The volume is equal to the side area multiplied by the length
What is the original volume of this wood
1.5m = 15m
0.16 × 15 = 2.4 (cubic decimeter)

The solution of the equation 1 / 2 x-3 X-1 = 1 / 2 is

Double six on both sides
3x-2 （x-1 ）=3
3x-2x+2=3
3x-2x=3-2
x=1

If a and B are opposite to each other, m and N are reciprocal to each other, and the square of K is equal to 4, then the value of 100A + 99b + MNB + K2 is ()
A. -4B. 4C. -96D. 104

∵ a, B are opposite numbers to each other, ∵ a + B = 0, ∵ m, n are reciprocal numbers to each other, ∵ Mn = 1, and the square of ∵ K is equal to 4, ∵ original formula = 100A + 99b + B + 4 = 100A + 100b + 4 = 100 (a + b) + 4 = 0 + 4 = 4

The positions of rational numbers a, B and C on the number axis are shown in the figure. The reduction result of the formula | a | + | B | + | a + B | + | B-C |, is______ ．

From the number axis, a < 0, b > 0, C < 0, | a + b > 0, B-C > 0, | a | + | B | + | a + B | + | B-C | = - A + B + A + B + B-C = 3b-c. so the answer is: 3b-c

The new year's Day is coming. In order to promote a certain commodity, the merchant gives a 75% discount on the original retail price, and then gives a 20% discount. At this time, the retail price is 300 yuan. If you sell it at this price, the store still has 25% profit
(1) What's the retail price of this product before it's on sale?
(2) What's the price of this commodity?
(3) If this kind of commodity is sold according to the original price, what is the profit rate!

(1) Let's suppose that this product is sold for X Yuan before discount
75%X*80%=240 400
(2) Let the purchase price be x yuan
（1+25%）X=240 192
（3）（400-192）/192=108%（108.3%）

0.000043 mm =? Nm (expressed by scientific counting method)

If 1nm = 1x10-9m, 1mm = 1x10-3m, 0.000043mm = 4.3x10 ^ - 9m, 0.000043mm = 4.3nm

OA, vertical ob, angle BOC = a (o degrees)

45°.
Angle EOF = angle EOC + angle COF = 1 / 2 (angle AOC + angle BOC)
=1 / 2 angle AOB = 45 degree

In the parallelogram ABCD, ad = 2Ab, extend AB to both sides, make AE = BF = AB, prove EC ⊥ FD
It is helpful for the responder to give an accurate answer

Ad = 2Ab -- AF = ad -- angle ADF = angle AFD
Because it is a parallelogram, so: angle FDC = angle AFD
Estimated angle ADF = angle FDC