A piece of iron wire, just to make a 8 cm long, 6 cm wide, 4 cm high cuboid frame, If you use this wire to make a cube frame, how long is the edge of the cube?

A piece of iron wire, just to make a 8 cm long, 6 cm wide, 4 cm high cuboid frame, If you use this wire to make a cube frame, how long is the edge of the cube?

(8+6+4)*4/12=6
A piece of iron wire is used to make a cuboid frame which is 8 cm long, 6 cm wide and 4 cm high. If the iron wire is used to make a cube frame, the edge length of the cube is 6 cm

The figure below is an expanded view of a cuboid. Find the surface area and volume of the cuboid. [unit: cm]

Length: 8 cm
Width: 4cm
Height: 6cm
Surface area: (8x4 + 8x6 + 4x6) x2 = 208 square cm
Volume: 8x4x6 = 192 CC

How long does it take to fly from the earth to the sun?

20 years

A paper tape with negligible gravity is clamped in the book. If the pressure of the book on the paper tape is known to be 2n, and the paper tape can be pulled out at a constant speed by pulling horizontally with F = 1n, the friction force on the paper tape is several n, and the dynamic friction coefficient between the paper tape and the book is what

Because the tape is pulled out at a constant speed
So the tape is balanced
In the horizontal direction, the paper tape is subject to tension and friction, so the friction is equal to the tension of 1n, FMO = u * supporting force = u * 2 = 1
So u = 0.5

After a parallelogram is cut and complemented, it is a square. The perimeter of the square is 16 cm. The area of the parallelogram is______ Square centimeter

16 △ 4 = 4 (CM), 4 × 4 = 16 (cm 2). Answer: the area of parallelogram is 16 cm 2

A simple method is used to calculate: 84 4 / 19 times 1.375 + 105 5 / 19 times 0.9

The original formula = (1 / 21 * 4) * 1.375 + = (1 / 21 * 5) * 0.9
=21 and 1 / 19 * (4 * 1.375 + 5 * 0.9)
=21 and 1 / 19 * (5.5 + 4.5)
=1 * 10 of 21 and 19
=210 10 / 19

Simplification: (1 + sin2a) / (COS & sup2; a-SiN & sup2; a)

(sina+cosa)^2=sina^2+cosa^2+2*sina*cosa=1+sin2a
cos2a-sina=(cosa+sina)*(cosa-sina)
So (1 + sin2a) / (cos2a-sin2a) = (Sina + COSA) / (COSA Sina) = (Tana + 1) / (1-tana)

As shown in the figure, the width of the "Hui" shaped road is 1 meter, and the length of the whole "Hui" shaped road is 8 meters and the width is 7 meters. A person walks along the center of the road from the entrance point a to the end point B, and he walks ()
A. 55 m B. 55.5 m C. 56 M D. 56.5 M

According to the analysis of the meaning of the topic, the distance from outside to inside is: length is 7.5, 7, 6, 5, 4, 3, 2, width is 6, 5, 4, 3, 2, 1, 0.5, so he walked 56 meters

Write two ratios that are 7 / 9: () and ()

36:28

Let BN + 2 = 3 (Log1 / 4) an (n ∈ n *) satisfy CN = an * BN
(1) Find the general term formula of sequence {BN}; (2) find the first n term and Sn of sequence {CN}
Answer to the process, detailed ~!

(1) From the meaning of the title, we can get the conclusion
an=(1/4)^n;
Then:
bn+2=3*log(1/4)an=3n;
So:
BN = 3n-2, is the arithmetic sequence;
(2) From the condition CN = an * BN, we can get that:
Cn= (1/4)^n*(3n-2)=3n*(1/4)^n-2*(1/4)^n
Let the sum of the first n terms of cn be SN
Sn=3[1/4+2*(1/4)^2+…… +n*(1/4)^n]-2*(1/4+(1/4)^2+…… +(1/4)^n);
Let PN = 1 / 4 + 2 * (1 / 4) ^ 2 + +n*(1/4)^n; --------(1)
The results are as follows:
1/4*Pn=(1/4)^2+2*(1/4)^3+…… +n*(1/4)^(n+1); ------(2)
(1) (2) the results were as follows
3/4 Pn=1/4+(1/4)^2+(1/4)^3+…… +(1/4)^n-n*(1/4)^(n+1)
= 1/3*(1-(1/4)^n)- n*(1/4)^(n+1)
So Sn can be deformed as:
Sn=3[1/3*(1-(1/4)^n)- n*(1/4)^(n+1)]-2*[1/3*(1-(1/4)^n)]
=1/3*[1-(1/4)^n]-3n*(1/4)^(n+1);
[note] in the calculation of Sn, the dislocation subtraction method is used. I remember that this method is used in the calculation of the sum of equal ratio Series in the textbook;