Key equations and simple arithmetic problems in primary school. Important, don t be a piece of cake.

Short-form arithmetic problem: additive associative property: a+b+c=a+(b+c) multiplicative associative property: a b c a (b c).

Addition commutative law: a b b a multiplicative commutative law: a b b a subtractive associative law; a b c a b c division associativity; a÷b÷c＝a÷﹙b×c﹚

multiplicative distributive law; a b c = a b a c sibling commutative law; a b c=a c b or a b c=a c b In short, it is necessary to have a symbolic exchange

Emphasis equations. Minus minus = difference difference minus = minus minus - difference = minus.

Addition Addition = sum and - addition = another addition.

Divisor Divisor Quotient Divisor Dividend Quotient Divisor Quotient Divisor.

Multiplier Multiplier Product Product Multiplier Another multiplier.

Fraction 1 Fraction 2 Fraction 1 Fraction 2 reciprocal.

Haven't you taken the graduation exam yet? I took the exam on June 9th).

x－b a=2－x－a b(a+b≠0).

Observe the characteristics of the equation structure, and tell us how to solve the equation.

Answer: This equation contains fractions, you can remove the denominator first, and convert the equation into a one-dimensional equation with letter coefficients.

of the general form. In equation deformation, the known condition a+b≠0

Solve the denominator and multiply both sides of the equation by ab.

b(x b)=2ab a(x a), remove the parentheses, get.

bx b2=2ab ax+a2, move the term, get.

ax+bx=a2+2ab+b2

Merge similar items to obtain.

a+b)x=(a+b)2.

Because a+b≠0, x=a+b

It is pointed out that ab≠0 is an implicit condition, because the letters a and b are the denominators of the two fractions in the equation, so a≠0 and b≠0, so ab≠0

The ratio of the number of girls in the fifth grade of the experimental primary school to the class size was 7:15. There are 120 boys in the fifth grade, how many are girls?

It would be better to suggest that you can buy some exercises.

Simplified: 8 17 + (9 17).

45 rides.

99999 times 77778 + 33333 times 666661991 squared - 1990 squared.

4 times 5 1 + 5 times 6 1 + 6 times 7 1....39 times 40 119 and four-sevenths - 56 and two-fifths + 80 and three-sevenths - 43 and three-fifths of the equation:

One. x+y=25 y+z=31 x+z=28 two. 2x+y+2z= x+3y+4z= y=4ziii.

x+y=27 y+z=33 x+z=30 four. 2a+3a-c=12 3a+2b+c=13 a+b+2c=75. x+y=z 2x-3y+2z=5 x+2y-z=32/1y-41/10=150%

4(x-(2/3x+6))=2/3x+6

3/5)/[x/36+x/45)*(1+1/5)]+2/5)/[x/36+x/45)*(1+1/5)-50]=18

Question 1:

Question 2: Question 3:

Question 4: Question 5: 3x+

Solution: 3x 25=85

3x＋25－25=85－25

3x=603x÷3=60÷3

x=20 Question 6: (x-8).

Solution: (x-8).

x-8=x－8＋8=

x=Question 7: 8(x-7)=24

Solution: 8x 56=24

8x－56＋56=24＋56

8x=808x÷8=80÷8

x=10Question 8: 34x-5x+48=106 Solution: 29x 48=106

29x＋48－48=106－48

29x=58

29x÷29=58÷29

x=2 choose me!

Now this kid can't do it.,,But the computer definitely does.,,And know how to ask on the Internet.,,Hey, when I was in elementary school, I didn't know what a computer was. To be honest I don't know how to explain this ,,, ...

I'll solve the equation :,

3x+solution: 3x+25=85

3x=85-25

3x=60x=20

x-8) solution: x-8=12*

x-8=x=x=

8（x-7）=24

Solution: 8x 56=24

8x－56＋56=24＋56

8x=808x÷8=80÷8

34x-5x+48=106

Solution: 29x 48=106

29x＋48－48=106－48

29x=58

29x÷29=58÷29x=2

1. Design scheme: take the center of the circle in the middle of the turntable, draw a line from the center of the circle, so that the turntable is divided into 3 fans, and the area of one of the fans accounts for 3 5 of the area of the turntable, and write 2 on this fan;

The area of a sector occupies 1 4 of the area of the turntable, and 3 is written on this sector;

The rest of the sector is written 1 on it.

2. Each person has to shake hands with 5 other people, and the number of times to be counted has to be divided by 2

Column: 6*(6-1) 2=15 times.

3. The second week dug is equivalent to the 7 9 of the first week, which is exactly 300 meters less than the first week, that is.

1-7 9=2 9 in the first week is 300 meters.

Then 300 (2 9)=1350 meters were dug in the first week.

The ratio of the first week to the total length was 3:8

The total length is 1350 (3:8) = 3600 meters.

4. Solution: Let the number B be x, then.

The number A is 4x, and the number C is 4x-1

The average is (x+4x+4x-1)=14 and 2 3=44 3

The solution is x=54x=20, and 4x-1=19

Answer: The number A is 20, the number B is 5, and the number C is 19

5. "All have that full stop referring to the decimal point, right?"

Correct, the equation holds.

6. "6 divide by the quotient of the sum obtained" that is.

Multiply again"7. One + 3 1 7 divided by ( 9 1 4 times 6 2 7 - 6 2 7 times 7 7 1 4).

3 and 1 7 divided by 6 and 2 7 times (9 and 1 4 - 7 and 1 4)].

3 and 1 7 divided by (6 and 2 7 times 2 and 1 4).

3 and 1 7 divided by (99 7).

4 7 - 10 and 3 7 -

2 --25 Multiply.

4 7 - 10 and 3 7 -

equations"="Knowledge of left-right sub-transformation methods.

Example: 3 x 4 = 12

Divide both sides by 4 at the same time, ie.

The deformation is 3=12 4 (this step is compared with 3*4=12, is it that one side is multiplied by the other).

In short: in order to ensure that the equation is correctly deformed, both sides of the equation must be multiplied and divided by a number at the same time.

1.Design 20 grids, 2 numbers put 12 grids, 3 put 5 grids, others put 1In fact, it is the least common multiple of 5 and 4 multiplied by their respective ratios.

2.In this list, let 6 people be a b c d e f, arrange abcdef horizontally, arrange abcdef vertically, and draw a diagonal line in the middle (i.e., aa, bb, cc, dd, ee, ff).I don't know if you understand what I mean.

3.Let the full length be x, then 3x 8-(3x 8)*(7 9)=300, unraveling x=3600

4.Let x,y,z (x+y+z) 3=44 3 (i.e. 14 and 2 3).

x y=4 x-z=1 is fine, x=20 y=5 z=19

5.False, one is an integer and the other is a real number, there is a difference.

6.This question is a bit winding, I didn't understand it. It should be 175 12 = 14 and 7 12

7.One: Press your title.

--Score line) = ---

Two. The result above the score line is 77

The result below the cut-off score is 100

The result was 111 10000

Bottom"="Knowledge of the left-right sub-transformation method is cross-multiplication and division.

For example: 5 1-=- According to this principle, x is the denominator on the left, moved to the right as the numerator, multiplication, and vice versa.

If you are x 3, the result is x = 5 * 3 = 15, you know, you have to listen carefully in class.

, because the least common multiple of 5,4,20 is 20

So the turntable is divided into 20 equal parts.

Forehead... I'm in the sixth grade, though. But I'm a Beijinger.