Math problems junior one, one dimensional equations to detail the process .

The original plan was to excavate x 10,000 cubic meters of earth and stone per day.

2x+3(2x+1)=

8x+3=8x=x= 10,000 cubic meters.

After the increase, 2x+1=2* 10,000 cubic meters.

Equation idea: x is the original speed, 2x is the workload of 2 days, (2x+1) is the later speed, that is, 10,000 cubic meters more than 2 times the original, 3 (2x+1) is the workload of 3 days of work at the later speed, and the sum of the two is the total workload of 10,000 cubic meters.

The original plan was to excavate x 10,000 cubic meters of earth and stone per day.

2x+（2x+1）×（5-2）=

2x+6x+3=

8x=x=Excavate earth and stone every day after additional personnel and equipment: 2x+1=20,000 cubic meters.

Solution: The original plan was to dig x 10,000 cubic meters per day. Dig for 3 days after deploying additional personnel and equipment.

2x+3（2x+1）=

2x+6x+3=

8x=x=A: The original plan was to dig 10,000 cubic meters per day, and after the deployment of additional personnel and equipment, 10,000 cubic meters was excavated.

First of all. The original plan was to excavate x 10,000 cubic meters of earth and stone per day.

After that. According to the title: After the deployment of additional personnel and equipment, 2x+10,000 cubic meters of earth and stone will be excavated every day.

And then again. The title says: I originally planned to do it for 2 days, but I did it for 5 days, so I did it for 3 days after the increase.

So Le. List the equation: 2x + 3(2x+1) = the final calculated solution is.

The original plan was to excavate 10,000 cubic meters of earth and stone per day, but after the deployment of additional personnel and equipment, 10,000 cubic meters of earth and stone were excavated every day.

Solution: Arrange x people to work at the beginning of the set.

By the title, there is 4x+8(2+x)=52

This results in 4x+16+8x=52

Shift, you get 12x=52-16

Get 12x=36

Divide the left and right sides of the equation by 12 at the same time

Get x=3 i.e. 3 people work at the beginning, then 5 people work.

Set up by x people first.

4x/52+8(x+2)/52=1

4x+8x+16=52

12x=36

x = 3 people. A: Arrange 3 people to do it for 4 hours first.

Solution: To set up a specific situation, X people should be arranged to work first;

1-4x×1/52=(x+2)×8/52；

or 52-4x=(x+2) 8;

Solution: x=3

Set x people to do it first.

Think of this event as a unit 1, 1 person does 52 hours, that is, one hour does 1 52 The equation is: (x 52)*4+[(2+x) 52]*8=1 solution x=3

Analysis: It takes 52 hours for one person to complete the question, so the work efficiency is 1 52 Solution: If you should arrange x people to work first.

4x/52+8（x+2)/52=1

4x+8x+16=52

12x=36x=3

X people should be assigned to work first.

4x/52+8（x+2）/52=1

x=3 should be assigned 3 people to work first.

Shouldn't you use a binary equation for the first year of junior high school?

1: Solution: Let the velocity of A be x and the velocity of B be y

180（x-y）=400

40（x+y）=400

The solution is x=55 9

y=35/9

Answer: 2: The straight line between two points is the shortest.

The arch is stable and evenly stressed.

3: Minute hand 54° hour.

1 will not, 2, between two points, the shortest line segment. Visitors who walk on the curved bridge stay longer and spend a long time watching. 3, 54 ,

1, The same direction is the problem of catching up, is the speed difference between the two, how much is the difference? It is a lap of the sports field, and the time it takes is 3 minutes; The reverse is a matter of encounter, and it is the sum of the speeds of the two, and what is it? It's still a lap of the stadium, and it takes 40 seconds.

Let the velocity of A be x, B can be set by the relation just now, for example, with the relationship of the velocity difference, B is x-400 3, and then the equation can be listed by using the relationship between the velocity and the other.

2.Understand for yourself.

3.The angle at which the minute hand rotates per minute is: 360 degrees for 60 minutes; The angle at which the hour hand rotates per hour is: 360 degrees 12 hours = 30 degrees, and the angle of rotation per minute is: 30 degrees 60 minutes.

1.Analysis: The same direction is the pursuit problem, and the reverse direction is the encounter problem.

2.Analysis: omitted.

3.Analysis: A large grid of the clock is 30 degrees, and a small grid is 5 degrees. The hour hand travels one hour in one large square, which is 60 minutes, and the number of degrees traveled by the hour hand can be obtained by using the first 60 degrees of the first 30 degrees, and then multiplied by the corresponding number of minutes.

Remember, I can only tell you the way of thinking, as the saying goes, and I hope you can figure it out yourself. ）

The solution burned for x hours, then.

1-x/4=(1-x/3)*2

12-3x=24-8x

5x=12x=12/5

Burned for 12 to 5 hours.

That is, 2 hours and 24 minutes.

Idea: The equivalence relationship of this question is that the length after burning is the same length and the candle before burning is the same length, so that it can be burned in units of 1, 4 hours, then every hour burns 1 4, burns x 4, then it will burn x 4, and the remaining length is 1-x 4

Let the distance from A to B be X kilometers, 3 hours and 20 minutes, and 10 3 hours.

then x (10 3) = (x-120) 2

3x/10=x/2-60

3x=5x-600

2x=600

The distance from x=300a to b is 300 km.

Idea, the equivalence relation of this question is velocity. And velocity = distance Speed of time before shortening = x 3 hours and 20 minutes of time taken Speed after shortening = distance after shortening, i.e. (x-120), divided by two hours.

I've written down your serial number, and I'll make it for you when I adopt it.

1 question will not! 2. （1）.

20-5=15 (only) Set teacup 2 yuan 15x2 = 30 (yuan) 5x5 = 25 (yuan) 25 + 30 = 55 (yuan) (2) 5x5 = 25 (yuan) 25x90% = yuan) 20x2 = 40 (yuan) 40x90% = 36 (yuan) 36 + yuan).

A: Method (1) should be used.

Question 1 will not - 2 （1）.

20-5=15 (only) Set teacup 2 yuan 15x2 = 30 (yuan) 5x5 = 25 (yuan) 25 + 30 = 55 (yuan) (2) 5x5 = 25 (yuan) 25x90% = yuan) 20x2 = 40 (yuan) 40x90% = 36 (yuan) 36 + yuan).

A: Method (1) should be used.

According to the question: (1) (4x 20) 4 (6x 20) 5 solution x 45 (2) (4x 20) 4 2 (6x 20) 5 solution x 35 (3) 4x 20) 4 2 (6x 20) 5 x 55 Answer: (1) If the actual work of the two groups of workers is equal in this month, then the average quota per person in this month is 45 pieces.

Solution: (1) Set the per capita quota in March to be x pieces According to the question: (1) (4x 20) 4 (6x 20) 5 solution x 45 (2) (4x 20) 4 2 (6x 20) 5 solution x 35 (3) 4x 20) 4 2 (6x 20) 5 x 55 Answer:

1) If the average workload of the two groups of workers is equal for the month, then the average quota for the month is 45. (2) If the average workload of the workers in Group A is 2 more than that of Group B, then the average quota for this month is 35. (3) If the average workload of the workers in Group A is 2 less than that of Group B, then the average quota for this month is 55.

10 Teacher Zhang's family used more than 20 tons of water in May.

Set to x tons. 10×x=21

Mr. Zhang's family used 21 tons of water in May.

1. The analysis shows that if the water consumption is less than 10 tons or 10 tons, the maximum charge is yuan; 10 20 tons, the maximum charge is yuan.

Mr. Wang's home must have more than 20 tons of water. (Therefore, the total water consumption is 1 + 10 + 10 = 21 tons.)

2 If the rental price of a 45-seater passenger car is X yuan, the rental price of a 60-seater passenger car is (x+200).

According to the title, 2x+4(x+200)=5000 x=700 (yuan), that is, the rent of a 45-seater passenger car is 700 yuan, and the rental price of a 60-seater passenger car is 900 yuan.

Solution: Yuan).

cubic meters) 64 (10-7) = 21 surplus 1

50-22=28 (households).

A: This month, there are up to 28 households that use less than 7 cubic meters of water.

Set A clothing x yuan B clothing (500-x) yuan (because A and B two pieces of clothing, the number of pieces is not considered).

Therefore, from the meaning of the title, the actual sales of clothing A are: (150% x) times 90% = 135% x.

Similarly, the actual sales of clothing B are: (140% (500-x)) times 90% = 126% (500-x).

And the profit is: 157, the cost: 500. So: the equation is: 126% (500-x ) + 135% x ) -500 = 157

Solution: {x=300.}

Therefore: 300 yuan per piece of clothing A, 500-300 = 200 yuan per piece of clothing B.

Let the cost of clothing A be x yuan and the cost of clothing B is (500-x) yuan, then, (1+50%)*90%x+(1+40%)*90%*(500-x)-500=157

The solution is x=300, so, 500-x=200

Solution: Suppose that the cost price of clothing A is $x, then the cost of clothing B is (500 x). 150%x＋140%（500―x)]×90%=657

The result of the solution is that the cost of clothing A is 300 yuan, and the cost of clothing B is 200 yuan.

Let the cost of A be $x, then the cost of B is (500-x) yuan.

Solve it.

Let A be x and B be y and the equation can be listed according to the conditions.

x+y=500

It can be solved with x=300

y=200

Let the cost of A be x, then the cost of B is 500-x x(1+50) 90+(500-x).

1+40％）×90％＝500+157x×150％×90％+（500－x）×140％×90％＝657

135 x + (500-x) 126 657 x 300 yuan then the cost of B 500-300 200 yuan.