I want to ask questions from the 7th grade of math with answers .

Go buy a tutorial book.

19 Solving Equations:

20 Solve the equation: (x-1)- 3x+2)= - x-1).

21 As shown in the figure, there are many information cards neatly pasted on a display board, these cards are the same size, and three squares of blank space are exposed between the cards, and the short side length of the known cards is 10 centimeters with a diagonal line in the figure, and if you want to match three ** to fill the gap, you need to match the size of **

22 A three-digit number, the number in the hundred digit is greater than the number in the ten-digit by 1, and the number in the single digit is less than three times the number in the ten-digit place.2 If the order of the three digits is reversed, the sum of the three digits and the original three digits is 1171, find the three digits

23 It is understood that the train fare is determined according to the method of "" It is known that the total mileage from station A to station H is 1500 kilometers, and the reference price of the whole journey is 180 yuan The following table is the mileage from each station to station H along the way:

Station name a b c d e f g h

Each station to station H.

Mileage (m) 1500 1130 910 622 402 219 72 0

For example, to determine the train fare from station B to station E, the fare is = yuan).

1) Find the train fare from station A to station F (the result is accurate to 1 yuan).

2) Passenger Aunt Wang took the train to her daughter's house, and after two stops on the train, she took the ticket and asked the attendant: "Am I almost at the station?" The attendant saw that the fare in Aunt Wang's hand was 66 yuan, and immediately said that the next stop would be there Please ask Aunt Wang where she got off the train (ask to write out the answer process).

24 The admission fee for a certain park** is stipulated in the following table:

Number of ticket purchasers: 1 50 people, 51 100 people, 100 people or more.

The ticket price is 5 yuan and 4 yuan.

A total of 103 people in class A and class B of a school (of which the number of class A is more than the number of class B) to visit the park, if the two classes are separately purchased by class, a total of 486 yuan will be paid

1) How much money can be saved if two classes are combined and buy tickets as a group?

2. Multiple choice questions.

15 (1) The following statement is correct (

a) the number with a larger absolute value is larger;

b) the number with the larger absolute value is smaller;

c) two numbers with equal absolute values;

d) Equal: The absolute value of two numbers is equal.

16 a0 is known, and |a|>|b|>|c|, then |a|+|b|-|c|+|a+b|+|b+c|+|a+c|Equal to (

a.-3a+b+c

d.-a+3b-3c

17.The following conclusion is correct ()a

Approximate numbers are the same as significant figures.

b.An approximate number is a number that is accurate to the single digit, and its significant figure is cApproximate numbers have 5 significant figures.

d.The approximate number 5,000 is the same as the approximate number 5000.18 If two rational numbers are added together, and if the sum is smaller than any of them, then both additions ()(a) are positive.

b) are all negative.

c) Opposite numbers to each other.

d) Variant name. 19.If there is a rational number ().

a.When dNone of the above is true.

20 If the sum of two non-zero rational numbers is positive, then both rational numbers are ()(a) are both positive.

b) At least one of them is positive.

c) A positive number is greater than a negative number.

d) The positive number is greater than the absolute value of the negative number, or both are positive.

3. Calculation questions. 21.Find the values of (-48) 6-(-25) (4)(2);

Solution: Let the train speed be x m s

v A = v B =

A and the train are opposite each other, and it is a matter of encounter.

Distance = train length = (1+x)*15

A and the train are going in the opposite direction, and it is a matter of pursuit.

Distance = train length = (x-1) * 17

1+x）*15=（x-1）*17

15x+15=17x-17

2x=32x=16

So, train length = (1 + x) * 15 = 17 * 15 = 255 (m) Answer: The train length is 255m.

If you don't understand, you can ask, o( o

Solution: Let the train speed be x

15×(x+1)=17×(x-1）

15x+15=17x-17

2x=32x=16m/s

So train length = 15 (16+1) = 255m

set, the length of the car x km, the speed of the car is b km h.

Armor. 15b+

Second. Solution x=. Pay attention to the units.

Let the train length be x km

17s=17/60h.15s = x divided by 17 60 plus minus

Solve x=

(1) There are 20 people who fail (2): 16 people with flower pots, 8 people with trays.

The current number of sides is 2520 180 + 2 = 16

After removing an inside corner, his number of sides may be added by 1, subtracted by 1, or unchanged.

So it turned out to be a 15-sided or a 16-sided or a 17-sided.

Let the original polygon be an n-sided.

Then (n-2)*180-(n-2)*180 n=2520

Is it a mistake, equal to 2720? For an 18-sided shape?

15-sided or 17-sided.

On the same floor, do not go to the inner corner is 16 sides. Removing an inside corner is actually adding or subtracting an angle.

1. (1) The correct of the following conclusions is ( ).

a.Divide by 3 on both sides of equation 3a-6=3b+5 to get the equation a-2=b+5

b.Subtract x-3 from both sides of the equation 7x=5x+3 to get the equation 6x-3=4x+6

c.Divide by both sides of equation -5= to get equation x=

d.If -2=x, then x=-2

2) Solve equation 20-3x=5, and the correct one after shifting the term is ( ).

a.-3x=5+20 d.-3x=-5-20

3) Solve the equation -x=-30, and the coefficient is 1, and the correct one is ( ).

a.-x=30 d.

4) To solve the equation, the following deformations are easier ( ).

a.Multiply 20 on both sides of the equation to get 4(5x-120)=140

b.Divide both sides of the equation by .

c.Remove the parentheses to get x-24=7

d.Equation arrangement, got.

Example 2(1) If the equation 3nxm+2y4 and -mx5yn-1 can be combined into one term, try to find the value of m+n.

2) The number of the following merge errors is ( ).

5x6+8x6=13x12②3a+2b=5ab③8y2-3y2=5④6anb2n-6a2nbn=0

a) 1 (b) 2 (c) 3 (d) 4.

Example 3Solve the following equations.

1)8-9x=9-8x (2)

Solution: A=1 is obtained from (a-1) 2+丨b+2丨=0, and the sum of the distances between point c and points a and b is 11

丨c-1丨+丨c+2丨=11

c = -6 or 5

a(bc+3)-c squared -3 (a-1 9c squared) = (-2c+3)-c 2-3(1-1 9c 2) = -2 3c 2-2c = -12 or -80 3

Solution: Because (a-1) 2+丨b+2丨=0 , a=1, b=-2

丨c-1丨+丨c+2丨=11

a(bc+3)-c 2-3(a-1 9c2) = -12 or -80 3

Accept it, thank you!

Good luck with your studies!

Because (a-1) 2+丨b+2丨=0 gives a=1, b=-2, and because the sum of the distances between point c and points a and b is 11

丨c-1丨+丨c+2丨=11

c = -6 or 5

a(bc+3)-c squared -3 (a-1 9c squared) = (-2c+3)-c 2-3(1-1 9c 2) = -2 3c 2-2c = -12 or -80 3

You start with 2000-800=1200, and he says that the part over 800 yuan will be taxed at 14%, and he will use 1200x14%.

Solution: 1 First find out how many times the speed of the speedboat is the speed of the current.

96-24+96) 24=7 (times).

2 When the speedboat returned to place a, the raft went a few kilometres away.

96 (7+1)+96 (7-1)=28 (km)3 The distance traveled by the wood divided by the time the raft traveled equals the speed at which the raft walked.

28 14 = 2 (kmh).

4 then the speedboat speed is.

2 7 = 14 (kmh).

A: The speed of the speedboat in still water is 14 km h and the speed of the current is 2 km h.

The speedboat travels 96 kilometers and then returns to point A, which takes 14 hours. This yields: 96 (V-water + V-boat) + 96 (V-boat-V-water) = 14

On the way back, the speedboat encountered the raft at a distance of 24 kilometres from point A. The time spent on both is equal, from which we get:

96 (V water + V boat) + (96-24) (V boat - V water) = 24 V water can be solved by the above two formulas, V water = 2 km h and V boat = 14 km h.