Urgently, some math application problems in the first year of junior high school

1.Set the number of workers in the production of round and square respectively x, y, by the inscription.

x+y=42,120x=80y*2

The solution is x=18, y=24

2.Let Xiaojun run x laps, and Xiao Ming ran (x+1) laps at this time, and the time they experienced is the same by the title, then 400x 5=400(x+1) 6, and the solution is x=5

3.Let this workload be a, then everyone's work speed is a 32, and then the number of people who need to arrange work is x, and x*(a 32)*2+(x+1)*(a 32)*4=a 2, and the solution x=2

4.Let a total of x people, from the meaning of the question (x 40) + 4 = x 30, solve the problem of x = 480 first ask what to set what, and then look at what kind of equation the question gives by the question, it is very simple to find out the equation problem, and it is not difficult to study more such questions

1. Because two rectangular iron sheets are matched with one rectangular iron sheet, the number of round iron sheets produced on the first day is twice the number of rectangular iron sheets.

Set up x people to produce round iron sheets, arrange y people to produce rectangular iron sheets, and list the equations according to the topic

x+y=42 （1）

120x=2*80y （2）

The solution: x=24 y=18

Therefore, 24 people should be arranged to produce round iron sheets and 18 people should be arranged to produce rectangular iron sheets.

2. Set Xiaojun to run x laps, and Xiao Ming ran (x+1) laps from the title, and the time they ran was the same, and the equation can be listed:

400x 5=400(x+1) 6, solution: x=5

3. If the workload is "1", then everyone's work speed is 1 32, and the number of people who need to arrange work is x, which can be obtained from the title

x*(1 32)*2+(x+1)*(1 32)*4=1 2, the solution: x=2

4. Set up a total of x people, which is derived from the title:

x/40)+4=x/30

Solution: x=480

1.Solution: If there are x people producing round iron sheets, there are 42-x people producing rectangular iron sheets.

120x = 2 times 80 (40-x).

There's nothing I can do about anything else.

Child, you should ask a teacher or someone older than you in your life so that she can explain it to you, so what's the use of only having the answer? Next time you still don't know!

If the original price of B is considered as unit 1, then A is.

If the percentage of price reduction of A is x, then the percentage of price increase of commodity B is 2x.

Columnable equations. x=2x=20/100

Answer: The percentage of price reduction for product A is 10 100The percentage increase for product B is 10,100.

Let the original price of commodity A be x, then the original price of commodity B is, the price of A is reduced by y, then B will raise the price by 2y, the sum of the unit price of commodity A and B before the price adjustment is:, and the sum of the unit price of commodity A and B after the price adjustment is: (x-xy)+(

The sum of the unit prices has increased by 2%:

Simplify, you can eliminate x:y=

That is, commodity A has dropped, and commodity B has increased its price by 5%.

Because the question is a required percentage, you can set Party B** to 1, and A** is then the total**.

Suppose the percentage change of Party A is xThat is, the percentage of Party B's increase is 2x, then the ** of A is 2x, and the ** of B is 2xThen you get the following formula.

The formula is solve.

x=10 i.e. A drops by 10% and B rises by 20%.

Solution: If the original price of commodity B is a constant, then the original price of commodity A is, the percentage of price reduction of commodity A is x, and the percentage of price increase of commodity B is 2x

The solution is x=10%, so the price of product A is reduced by 10%, and the price of product B is increased by 20%.

Solution: If the original price of B is x, then the original price of A is, and then the percentage of price reduction of A is y, then the percentage of price increase of B is 2y. Yes.

The sum of the original unit price of A and B is.

The sum of the unit prices after price adjustment is +x(1+2y).

Therefore, after the price adjustment, the sum of the unit prices of the two commodities A and B is increased by 2% compared with the sum of the original unit prices, that is.

x(1+2y)] =2%

Simplify. = 2%, got.

y=10% so.

The percentage of price reduction for product A is y=10%.

The percentage of price increase for product B is 2y=20%.

Hope it helps.

100 7 seconds.

That is, it takes seconds of evacuation time.

meters are accurate so the length of the meters can ensure safety.

It's simple.

It takes at least x meters to set up the fuse, and the time for the fuse to burn out must not be less than the time for the worker to run to a safe area, so there is.

x/>=100/7

7x>=11

x>=11/7

Solution: Let the length of the fuse be x.

x divided by 7m s

Solution: x 11/7

A: The length of the fuse should be at least 11/7 of a meter to ensure safety.

1.If a, b, and c are all even, there are three integers in a+b 2, b+c 2, and c+a 2.

2.If a, b, and c have an odd number and two even numbers, and a+b 2, b+c 2, and c+a 2 have an integer.

3.If a, b, and c have two odd numbers and an even number, and a+b 2, b+c 2, and c+a 2 have an integer.

4.If a, b, and c are all odd numbers, a+b 2, b+c 2, and c+a 2 have three integers.

So there is at least one integer.

Solution: (1) If the water fee payable is y, then.

0＜x≤8)

y={ (x＞8)

2) Because of 23>8, 42+

Answer: Xiaojie's family should pay the water bill in December.

Untie; (1) When 0 x 8; The water fee shall be RMB. When x 8; The water charge should be (x-8)*

Answer: Xiaojie's family should pay the water bill in December.

1.Set Dad to catch up with Xiao Ming and use x points.

According to the title, we get 180x=80x+80x5

Simplify, you get 100x=400

x=4Therefore, it took 4 points for Dad to catch up with Xiao Ming.

2.Because 180x4=720

So, when I caught up with Xiao Ming, it was still 280 meters away from the school.

The answer is supplemented. The first year of junior high school, page 191.

(1) When 0 x 8

The tax is x 8

Total cubic meters - 8) = the tax (2).

The area of the circle is 1 1 (unit: square centimeter).

Let the side length of the square be a, so a a = 1 1

a centimeter.

The area of the circle = 1*1*square centimeters.

Square side length = root number in centimeters.

s circle = let the side length of the square xx 2=