Use a 6-decimeter-long, 4-decimeter-wide rectangular sheet iron to make a 8-centimeter-deep cuboid uncovered sheet iron box (the welding joint is ignored). What is the volume of this sheet iron box? A book is 21 cm in length, 15 cm in width and 0.8 cm in thickness. If you give a book cover with 2 cm edges on the top, bottom, left and right sides, how many square centimeters of paper does it take to wrap the book?

1. (60-8 * 2) * (40-8 * 2) * 8 = 8448 (cm3)
2. (21 + 4) * (15 * 2 + 0.8 + 4) = 870 (cm2)

In order to make a cuboid box without cover with volume of 756cm3, height of 6cm and bottom length of 5cm more than width, what size of rectangular iron sheet should be selected?

Suppose the bottom of the box is xcm wide, then the length is (x + 5) cm. From the meaning of the question, 6x (x + 5) = 756, X2 + 5x-126 = 0, and the solution is X1 = 9, X2 = - 14 (not practical, omit). Thus, the length of the rectangular iron sheet is 2 × 6 + X + 5 = 26 (CM), and the width is x + 2 × 6 = 21 (CM)

Use a 50 cm long, 40 cm wide rectangular sheet iron to make a 10 cm deep uncovered rectangular box. How many cubic minutes does this box need
And what's the volume of this cuboid box?
More specific,

50 cm = 5 decimeters 40 cm = 4 decimeters 10 cm = 10 decimeters 5-1 * 2 = 3 (decimeters) 4-1 * 2 = 2 (decimeters)
3 * 2 * 1 = 6 (cubic decimeter) (3 * 1 + 2 * 1) * 2 + 2 * 3
=5*2+6
=16 (square decimeter)
A: the cuboid box has a volume of 6 cubic decimeters and a surface area of 16 square decimeters

Simple calculation of 1.625 * 1992 + 1992 * (3 / 8) - 1992

625 = 1 + 5 / 8
The original formula = (1 + 5 / 8) * 1992 + 1992 * (3 / 8) - 1992
=1992+（5/8)*1992+1992*(3/8)-1992
=1992*(3/8+5/8)
=1992

How to calculate 157 times 23 / 156?

157 times 23 / 156
=(156 + 1) times 23 / 156
=23+23/156
=23 and 23 / 156

Simple operation: 2004 × 20032003-2003 × 20042004

20032003 is equal to 2003 × 1000120042004 is equal to 2004 × 10001, the original formula is 0 = 2004 × 2003 × 10001-2003 × 2004 × 10001 = 0,

It is known that a = a + 2, B = a ^ 2 + 5, C = a ^ 2 + 5a-19, where a > 2

B-A=y=a^2-a+3
Consider the case of function y, whose axis of symmetry is x = 1 / 2
No intersection with X-axis (using discriminant)
So y is always greater than 0
So a is less than B

1,17,8,26,27,37,64,50,( ).
1,17,8,26,27,37,64,50, (), (answer: A: 65,24 B: 125,80c: 125,65 D: 65124

1,17,8,26,27,37,64,50, (), (from each other, we can see that if 1,8,27,64 are the third power of 1,2,3.4 respectively, then the next one is the third power of 5. 12517,26,37,50 are the second power of 4 + the second power of 1,5 + the second power of 1,6 + the second power of 1,7 + 1, then the next one is the second power of 8 + 165. The answer is C“

If the quadratic function y = (m-1) & sup2; + 2x has no intersection with the line y = X-1, the value range of M is obtained

Substituting y = X-1 into y = (m-1) x ^ 2 + 2x
x-1=(m-1)x^2+2x
(m-1)x^2+x+1=0
There is no intersection between two curves
Then the equation has no solution
Δ=1-4(m-1)

How much is the rectangle length divided by 2 width multiplied by 2 area?

The area remains unchanged
Because rectangle area = length x width
What you said is equivalent to: area = length / 2 x width x 2 = length x width
So, the area doesn't change