The sum of all integers whose absolute value is less than 5 is A：7 B：-7 C：0 D：5

The sum of all integers whose absolute value is less than 5 is A：7 B：-7 C：0 D：5

All integers with absolute value less than 5 have + - 4, + - 3, + - 2, + - 1,0
The sum of all integers whose absolute value is less than 5 is 0
C
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Summarize the primary school mathematics knowledge from three aspects (people's Education Press)
According to the three aspects of primary school mathematics knowledge points are summarized
1. Number and Algebra: focus on calculation and application
2. Graphics and geometry
3. Statistics and probability
It is better to control the number of words in each knowledge point at about 100 words, and add the corresponding serial number before each knowledge point.

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How many boxes can 20 apples be put into to ensure that at least one box has five or more apples?
Please explain why

One box, because if there are two boxes, it is likely that there will be 19 boxes and one box

60 mu = how many square meters? Is it 250 meters wide?

It's better to remember like this
60 mu = 3600 square feet = 360000 square feet = 40000 square meters
Width equals area divided by length: 40000 / 250 = 160m

The perimeter of a rectangular playground is 120 meters, connecting the midpoint of the long side, just dividing the playground into two squares. How many square meters is the area of the playground?

120 / 2 = 60 meters (because divided by two is the length of the widening)
Width: 60 / 3 = 20M (because it connects the midpoint of the long side, that is, the long side = 2 * width)
20 * 2 = 40m (according to the principle, length = 2 * width)
40 * 20 = 800 square meters (area = L * W)

1. A store launched the activity of "welcoming the Olympic Games". A TV set was priced at 35% of the purchase price, and then sold at a 10% discount. A taxi fee of 50 yuan was given to each set. In this way, each set could still make a profit of 208 yuan. How much is the purchase price of this TV set?
2. On Sunday, Wang Cheng rode to the library to read a book. He walked 200 meters per minute. After five minutes, he found that the tire was broken, so he had to walk with a cart. The speed of the cart was 2 / 5 (two fifths) of the speed of the bicycle, so he was 15 minutes late than the scheduled time
(1) How many minutes did Wang Cheng actually take from home to the library?
(2) How many kilometers is Wang Chengjia away from the library?
It needs to be calculated as yes, so can the comprehensive formula,

1. Set the purchase price as X Yuan
Price: (1 + 0.35) x price: (1 + 0.35) * 0.9 * x
Profit: (1 + 0.35) * 0.9 * x - x-50 = 208
1.35*0.9X-X=158
Just solve the equation of X
2. Cycling distance: 200 * 5 = 1000M
Trolley Speed: 200 * 2 / 5 = 80 m / min
Distance of cart: 15 * 80 * 200 / (200-80) = 2000 meters
Cart time: 2000 / 80 = 25 minutes
Actual use: 25 + 5 = 30 minutes
Distance between home and Library: 1000 + 2000 = 3000 meters

02 cubic meters, 4200 cubic decimeters, 4 cubic meters, 2 cubic decimeters, 4 cubic meters, 20 cubic centimeters

4《1=3《2

The addition and subtraction of mathematical integral on the first day of junior high school

Chapter 2 addition and subtraction of integral
Class: Name: Score:
1、 Fill in carefully, I believe I can fill in correctly (4 points for each question, 24 points in total)
1. In the following formulas - 3xy, A2-B2, 2x ＞ 1, - x, 0.5 + X, are integral, monomial and polynomial
2. The coefficient of a3b2c is, and the number of times is;
3.3xy-5x4 + 6x-1 is the subterm of X;
4. If - 2x2ym and xny3 are of the same kind, then M =, n =;
5.3ab-5a2b2 + 4a3-4 is in descending order of A;
6. The ten digit number is m, the one digit number is 3 less than m, the hundred digit number is 3 times of M, and the three digit number is
2、 Judge right and wrong, mark "√" for right and "×" for wrong (3 points for each question, 12 points in total)
1. All - 3, - 3x, - 3x - 3 are algebraic expressions （ ）
2. - 7 (a-b) 2 and (a-b) 2 can be regarded as similar terms （ ）
The two terms of 3.4a2-3 are 4a2,3 （ ）
4. The coefficient of X is the same as the number of times （ ）
3、 Where is the confidence? Just do it and you will know (7 points for each question, 42 points in total)
1．a＋（a2－2a ）－（a －2a2 ）； 2．－3（2a＋3b）－ （6a－12b）；
3．－{－[－（－a ）2－b2 ]}－[－（－b2）]； 4．9x2－[7（x2－ y）－（x2－y）－1]－ ；
5．（3xn＋2＋10xn－7x）－（x－9xn＋2 －10xn）； 6．{ab－[ 3a2b－（4ab2＋ ab）－4a2b]}＋3a2b．
4、 Evaluation after simplification (11 points for each sub question, 22 points in total)
1. When a = - find the value of the algebraic formula 15a2 - {- 4a2 + [5a-8a2 - (2a2-a) + 9A2] - 3A}
2. Given | a + 2 | + (B + 1) 2 + (C -) 2 = 0, find the value of the algebraic formula 5abc - {2a2b - [3ABC - (4ab2-a2b)]}
You do it first

Find regular answers: 5 + 3, 7 + 6, 9 + 9, 11 + 12 Find the result of the 1999 formula

According to the analysis and its conditions: the formula of 1999 is: 2 × 1999 + 3 + 3 × 1999 = 5 × 1999 + 3 = 9998 A: the result of the formula of 1999 is 9998

Adding an operation symbol between 100 and two 5S results in 19 and 10

（100-5）÷5=19
100÷（5+5）=10