Math problems all with equations are fast!!

1.The average speed of this car round trip is x kilometers per hour.

Average speed: (240*2)=(6+4)x

x 48 (km).

A: The average speed of this car is 48 kilometers per hour.

2.Set: Each cow eats 1 serving of grass per week.

Then: 27 cows ate 27x6=162 (portions) for 6 weeks and 23 cows ate 23x9=207 (portions) for 9 weeks

The grass grew (207-162) per week 3 = 15 (parts per week) and the grass initially had 162-6x15 = 72 (parts); Or use 207-9x15 = 72 (parts).

21 cows can eat 72 (21-15)=12 (weeks) as follows: let the total amount of grass be 1, the amount of grass per week is b, a cow eats grass in a week c, and 21 cows eat 27*c*6-6*b=1+6b in x days; 27. The grass eaten by cattle in 6 weeks minus the new grass grown every week in 6 weeks = the amount of original grass plus the amount of new grass grown in these 6 weeks 23*c*9-9*b=1+9b21*c*x-x*b=1+xb

3.Suppose a machine pumps the amount of water pumped in one minute in the unit "1" - if you want to use the equation, this step can be changed to x).

The water intake in one minute is: (3*40-6*16) (40-16)=1 unit.

It turns out that there is water in the pool: 3*40-40*1=80 units.

Then the pumping time of 5 machines is: 80 (5*1-1)=20 minutes.

Set up x number of students.

10x-22=428

x = 45 with x rooms.

6x-6*2=4x+6*2

x=12

Set the specified time to x days, and from the meaning of the question, 35*(x+1)=40*x-5 can be solved to obtain x=8

Therefore, the total number of pages in this book is 35*(8+1)=35*9=315So 315 39=

Round off to 1 (because the 8th day is the specified time) 39*7=273

315-273 = 42 pages.

Solution: Set the specified time to be x days, and the solution can be obtained from the meaning of the question 35*(x+1)=40*x-5 x=8

So the total number of pages in this book is 35 * (8 + 1) = 35 * 9 = 315So 315 39=

Round off to 1, 39*7=273

So it's 315-273=42 pages.

Since the speed of the two cars is the same, then let their speed be x kilometers, and know that the cars have traveled half of the whole journey in an hour, i.e., 1300 2 = 650 kilometers, then the equation can be listed to get x = 100, that is, their speed is 100 kilometers each.

It's their speed and, so.

100 each

Solution: A completes 1 50 per day B completes 1 15 per day, and B needs x days to complete.

So (1 50 + 1 45) 20 + 1 45 x = 11 45 x = 7 45

x=7 took a total of 27 days to complete < 30 days.

So it can be completed on time.

It will take x days to set up team B to complete, then.

1 50 + 1 45)*20+1 45*x=1 solution, x=7

That is, it will take 7 days to complete the project, 20 + 7 = 27 days < 30 days.

That is, it can be completed on time.

There are three water pipes A, B and C, and a single pipe can be filled with a pool of water for 5 hours; A and B are opened at the same time, and a pool of water can be filled in 2 hours; A and C are opened at the same time, and a pool of water is filled in 3 hours. Now open the three pipes together, after a period of time, the first pipe is stopped due to failure, and the pool is full 2 hours after the stop opening. Q: How long does it take to inject water into the tri-pronged water?

Solution: A water pipe 1 hour water injection of the whole pool, B water pipe 1 hour water injection: -= ;

1 hour water injection of water pipe: -= ;

Let the three-pronged water be filled with x hours, and according to the title, +x+2 ( =1

x+ =1x= x=

Answer: The three-pronged water is filled for hours.

From the meaning of the title, it can be seen that the efficiency of A is 1 5

The efficiency of B is (1-1 5x2) 2=3 10 The efficiency of C is (1-1 5x3) 3=2 15 (1 5+3 10+2 15).

1. Solution: Let this number be the solution equation.

x=152, solution: set the number of girls in class 5 and 3 to be x people. x+2x-9=45 Solve the equation to get x=18 45-18=27 for boys 3, x years ago, the mother's age is just 4 times the age of the son Hu or age.

50-x=(26-x) 4 Solve the equation to get x=184, Solution: Let there be x sunny days during this period 35x+22 (13-x)=403 Solve the equation to get x=95, Solution: Let there be x rabbits (x+13) 2-4x=16 Solve the equation to get x=5 There are 5+13=18 chickens.

1.Let this number be x: 3x-5=2x+10 x=152

Female x people: x+(2x-9)=45 x=18 female students 18 male students 27 male students 3Set x years ago, the mother's age was exactly 4 times the age of her son:

50-x=4（26-x） x=184.Let there be x sunny days: 35x+22(13-x)=403 x=95

There are x chickens: 2x-4 (x-13) = 16 x = 18 chickens have 18 chickens and 5 rabbits.

Solution: It is located x meters away.

x/80+1/6=x/60

x=240A: 240 meters away.

2.Solution: Set x kWh.

x=280280-140) * yuan.

A: 182 yuan should be paid.

3.Solution: Set x fold can be **.

4500x=(4500-3000)*

x=A: The lowest discount is possible**.

4.(1) Solution: Set the cost of x yuan.

1+ x=108

x=180135-108=27 yuan.

180-135 = 45 yuan.

A: Lost.

(1) If Lili walks for x minutes, then Lili walks x+10x*80 =60(x+10).

20x=600x=30

So there are a total of 2400 meters.

2) Set up a shared x kilowatt-hour of electricity.

140* +x-140)* =x*

3) Set up x discount.

4500*x =3000+3000*5%

4) Set the cost of the first piece to be X yuan.

135-x) =25% *x 135 -x = x x=135/

Let the cost of the second piece be Y yuan.

y-135) =25% y =135 y=135 The first piece earned 135 * =135 5 The second piece lost =135 3135 5<135 3 So it was lost.

a-x)= x x=a/

y-a)= y y=a/

a = a 5 The result is the same, both lose.

(1) Set the distance x meters, then the time taken is x 80, and the time taken by Xiaoli is x 60, and Xiaoli takes 10 minutes more than Xiaoming, so x 60-x 80 = 10

2) Assuming that the electricity consumption is x, obviously x>140, so there is (x-140) electricity consumption**. So [x is 280 degrees, so the electricity bill is 280.]

3) Set a minimum discount of x. Then (4500x-3000) 300=5%, you can find x (the discount statement needs to be noted.) If x= is calculated, it is discounted).

4) If the original price of the profit is x, then (135-x) x=25%, and if x=108, then the profit is 135-108=27 yuan. Let the original price of the loss be y, then (y-135) y=25%, calculate y=180, and the loss is 180-135=45 yuan, so it is a loss.

The second question in the back is also a loss, no matter how much A is.

The first middle school to the normal college is x meters.

x÷80＋10＝x÷60 x=24002.Solve the shared electricity in April x kWh.

140 x = 280 kWh.

The electricity bill is 280 yuan.

3.Set a minimum of x discount**.

4500x=3000 1 5 x So 7% off.