Math masters recently, ask for advice, math masters come to teach me

1.Originally, there were 6 faces, but after splitting, the area of 2 faces was increased.

The total area is 8*4*4=128 square decimeters.

2.After the split, there are 4 more base areas, which increases: 4 * 4 * 5 = 80 square decimeters.

3.Original surface area: 2*(10*8+10*6+8*6)=376 square centimeters.

The maximum is: 376 + 2 * 10 * 8 = 536 square centimeters.

The minimum is: 376 + 2 * 8 * 6 = 472 square centimeters.

1.128 corresponds to increasing the area of the two faces of the cube, i.e., (6, 2), 4, 2280 is equivalent to an increase of 4 widths.

3.The maximum is: 640 and the minimum is: 576

The original surface area is 10 8 6 480

After cutting, the surface area is increased by two times the cross-section, and the length and width, length and height, and width and height are increased by the three cutting methods respectively, and the maximum value can be known as the length and width, and the minimum value is the width and height.

The maximum sum of the surface area is: 480 + 10 8 2 640 The minimum is: 480 6 8 2 576

128 (square decimeter).

2. The part of the increased surface area is the extra four sides after cutting. Namely:

5 4 4 = 80 (square decimeter).

3. There are three ways to cut:

The surface of the original cuboid is: (6 8 + 10 6 + 10 8) 2 = 376 (square centimeters).

The first is to cut the long side, then the increased surface area is: 6 8 2 = 96 (square centimeters) The second is to cut the wide side, then the increased surface area is: 10 6 2 = 120 (square centimeters) The third is to cut the high side, then the increased surface area is:

10 8 2 = 160 (square centimeters), 160 square centimeters, 120 square centimeters, 96 square centimeters.

So, the sum of the surface areas of the two truncated boxes.

The maximum is: 376 + 160 = 536 (square centimeters) and the minimum is: 376 + 96 = 472 (square centimeters).

Bottom circumference = 10

2π r=10 r=π/5

Base area = r squared.

So volume = 250

2.2 kinds.

The first type of base circumference =

2 r=r=5 base area = r squared s=25

The second type of base circumference =

2 r=r=1 base area = r squared s=

If you teach it, it won't help you calculate.

The first question is to find the area of the square, because the square is surrounded by a cylinder, then the side length of the square is the perimeter of the base area of the cylinder, so that the radius of the cylinder can be calculated. And the height of the cylinder is also the side length of the square. The volume is simple.

The second question, because the length and width of the rectangle are different, the way you enclose them is also different. One is the perimeter with the width as the base area, and the other is the perimeter with the length as the base area. The perimeter is known, and the radius is known. In this way, the bottom area of the cylinder is also known.

1. Let the radius of the enclosed bottom surface be r, then 2pie*r=10, r=5 pie can be obtained, and the volume of the cylinder v=pie*r*r*r*10=25 pie=square centimeters;

2, 2 kinds of enclosure. If the width is used as the height circumference of the cylinder, the base area = square centimeters is calculated according to the algorithm in the above question; If the length is used as the height of the cylinder, the base area = square centimeters is calculated according to the algorithm in the above question.

Greater than 9000, abbreviated to two digits can be divisible by 11, it must be 99 so greater than 9845, less than 9944

Abbreviated to 3 digits divisible by 4, only 988 992

Divisible by 13, 9880 13 = 760

So the available values are 9880 9919

Odd number selection 9919

Rounded to two significant figures, divisible by 11.

That is: 99xx

A four-digit singular number, divisible by 13.

Yes: 9919,9945,9971,9997 is divisible by 4 when rounded to three significant figures.

Yes: 9919, 9997

Hello, first replace x 2 + y 2 - 4x + 1 = 0 with the standard formula of the garden!!

That is, (x-2) 2+y 2=( 3) 2, which means that it is a circle with a center of (2,0) and a radius of root number 3. You can draw a circle like this on paper.

Let y x=k, then the value of y x is converted to the maximum and minimum value of the slope formed by the line that has passed through the origin and the point on the circle!! (The maximum and minimum values are also obtained when the line y=kx is tangent to the circle!) ）

Let y-x=kTransform the problem into a problem of finding straight lines and circles!! (Here the slope of the line does not change, but the intersection with the x-axis or y-axis changes).

Let x 2 + y 2 = kIn this case, the maximum and minimum of the radius of the circle passing through the origin are found (the maximum and minimum values are usually obtained at tangent!). ）