The first year of math problems is here! Math problems on the first year of junior high school, math

The first batch to the train station takes 15 60 = hours, that is, 15 minutes, at this time people have walked for kilometers.

If the time it takes for the car to come back and meet the person is x hours, at this time the person has gone 5*x, and the car has gone 60*x, then there is.

60*x+5*x=

The solvable x=hour, which is approximately equal to.

It takes hours to come and hours to go back. The total time elapsed is hours.

Minute. So they were able to catch the train.

At this time, the second group leaves the railway station: s=15-(5*1 4)=At this time, the cars begin to return, assuming that they meet after v hours, then:

The solution is v = 11 for 52 hours.

The total time t=t+2v=1 4 +11 52+11 52=70 104 hours is approximately equal to 40 minutes.

So to be able to arrive.

Note: Because the distance traveled by the car when it returns is the same as the distance traveled by the second group of people, the speed remains the same.

So after receiving the second group, the travel time was also 11 to 52 hours.

Yes. Suppose that when the car returns for the first time and meets the second group of people, the distance traveled by the second group of people is x.

x 5=[15+(15-x)] 60 Find x=30 13 The time taken for the whole process is t:

t=*60=

Because <42 I can catch up.

Calculate the time for the first batch of passengers to arrive at the railway station: 15 60 = 1 4h is the distance traveled by the second group is: 5 * 1 4 = 5 4km At this time, the car turns around and the second group continues to move forward. Let them meet at x5 4 + (60 + 5) * x = 15

5+260x=60

x=11/52h

15-(5 4+5*11 52)] 60=11 52h (this is the time when the car meets the second group of people and then returns to the station).

The time shared by the second batch is 11 52 + 11 52 + 1 4 = 6 13h 42 minutes = 42 60 = 7 10h 6 13h<7 10h, indicating that the second batch can catch the train.

The time of the first batch to the railway station is 15 60 = 1 4h

The distance traveled by a person is 5*1 4=5 4km

The time when the car meets the second group of people is t

60*t+5*t+5/4=15

65t=55/4

t=11/(13*4)

At this time, the distance from the railway station is 15-5 4-5*t=60*t=11 (13*4).

The total time taken is 11 (13*4)+11 (13*4)+1 4=35 52h>42 60

Said that he couldn't catch the train.

∵ab//cd,ae//cf

bac= dca, eac= fca (two straight lines are parallel, the inner wrong angles are equal) and the two angles are subtracted to get:

bae=∠dcf

1. A two-digit number, the sum of the single digit number and the ten digit number is 9, if the new number obtained after the single digit number and the ten digit number are reversed is 9 greater than the original number, then the original two-digit number is -(d)-?

2. There are a total of 15 questions in a mathematics competition, 4 points are awarded for choosing the correct one, 2 points are deducted for choosing the wrong question, if a student scores 36 points, he chooses the correct question (11)? (Not a mistake).

3. The hearing plan for the tiered electricity price for residential electricity announced by a province is as follows:

The first level of electricity: the monthly electricity consumption does not exceed 210 kWh, ** yuan per kWh.

The second level of electricity: the monthly electricity consumption exceeds 210 kWh and does not exceed 350 kWh, and the price of each kWh is higher than that of the first gear.

The third level of electricity: the monthly electricity consumption exceeds 350 kWh, and the price of each kWh is higher than that of the first level.

For example, if a consumer consumes 400 kWh, he needs to pay the electricity bill.

210 multiplied by (multiplied by (yuan)

If calculated according to this plan, Xiaohua's electricity bill in May is yuan, please find out Xiaohua's electricity consumption in May. [Available Equations Available Formulas].

210 yuan, kWh electricity consumption = 210 + 52 = 262 kWh.

4. A batch of dormitories, if each room lives 1 person, 10 people cannot be arranged; If there are 3 people in each room, there will be 10 unoccupied. The number of rooms in this batch of dormitories is: (a).

5. Solve the equation: (solve it step by step).

Two-sevenths multiplied by (3y+7) = 2-three-two-y

Solution: 2 7 (3y+7) = 2-3 2y

Multiply 14) on both sides, 12y+28=28-21y

12y+21y=28-28y=0

In the first question, you can try each option or make the original tens of digits x, the single digit y, 10x+y+9=x+10y, and the answer is d.

In the second question, choose the correct x channel, choose the wrong (15-x) channel, 4x-2(15-x)=36, and solve x=11

The third question is the first single with the most advanced grid of yuan, and the second level is the most advanced grid of 189 yuan, so Xiaohua belongs to the second level.

The fourth problem of the degree makes the dormitory have x rooms, then the number of people is x+10=3 (x-10), and the solution of x=20 is two-sevenths of the fifth problem multiplied by (3y+7)=2-three-thirds y6 7y+2=2-3 2y

6/7+3/2)y=0y=0

(1)d

2) Solve the problem that he chooses x correctly: 4x-2(15-x)=36 x=11(3) assuming that Xiaohua's house is a first-level electricity consumption, then it is inconsistent with the assumption.

Assuming that Xiaohua's home is a second-level electricity consumption, and the discarded electricity consumption is x, then its electricity consumption in May is 210, and x=262 is obtained, so Xiaohuajia's electricity consumption in May is 262 kWh.

A yuan electricity bill and so on.

4)a5)2 7x(3y+7)=2-3y2 multiplied by 1412y+14=28-21y shifted on both sides at the same time.

33y=42

y=14/11

Question 1: Select D

Question 2: 11 questions.

The third problem is to solve the electricity consumption of Xiaohua's house in May is x degrees.

210 x - 210) gives x = 262

Question 4: Choose A

Question 5 2 7(3y+7) = 2 - 3 2y6 7y + 2 = 2 - 3 2y

6/7y + 3/2y = 2 - 2

6/7y + 3/2y = 0

y = 0

A11 assumes that Xiaohua's electricity consumption in May is x kWh.

210 x + x - 210） x （ =+ （x-210）x =

x=262, so Xiaohua's electricity consumption in May was 262 degrees.

a2/7 x (3y+7) = 2 - 3y/26y/7 + 2 = 2 - 2y/3

6y/7 + 2y/3 = 0y=0

First, d. Second, 11Third, 243Fourth, c. The last question is y=0

1.Analysis: If there are x cages, then if there are (4x+1) chickens or 5 (x-1) chickens according to the known conditions, the equation can be listed, and the result can be obtained by solving the equation

Answer: Solution: There are x cages, according to the question: 4x+1=5 (x-1), solution: x=6, 4x+1=25, answer: there are 25 chickens and 6 cages

2.Solution: Let the distance between point A and Beishan station be x, and the time for the car to drive to point A is y60y=18-x

60-4)y/(60+4)+y=x/4

Solution: x=2

Therefore, the distance between point A and Kitayama station is 2km

1.There are x chickens and y cages, according to the title:

4y+1=x

y-1）×5=x

Solution: x=25

y=6 so at least 25 chickens, 6 cages.

2.Let point A be X kilometers away from the starting point, and after the car returns from point A, it will meet group B students after t hours to get the system of equations according to the known conditions.

1. x 60 * 4 + 4t + 60t = x

2. x 60*4+4t+((18-x) 4-t)*60=18 According to the above equations, x=16km is obtained

Point A is 2km away from Kitayama Station

Let the speed be x A 2 hours 2 * 5 = 10 km.

That is, B travels 10 kilometers more than A.

The speed difference is x-2

B catches up with A no earlier than 1h at the earliest, and catches up with A no later than 1h15min.

Therefore, it should be less than or equal to 10 in 1 hour

1*(x-2)<=10

x<=12

1h15min=

The hour is greater than or equal to 10

x-2>=8

x>=10

So 10<=x<=122, A 50, B 100. Let the total salary be Z, type A person and type B person B. z=600a+1000b=600a+1000(150-a)=150000-400a。

It can be seen that the larger the a, the lower the z-value. A is up to 50, and z is at least 3