Mathematics scheme design application problems for the first year of junior high school

1) There is a title to obtain: 200 for drinking water and 120 for vegetables

Suppose car A x car and car B car y.

x+y=8,40x+20y>=200,10x+20y>=120 to get 4>=x>=2

x=2,y=6; x=3,y=5;x=4 and y=4.

2) A 2x400+6x360=2960

2. 3x400+5x360=3000

3. 4x400+4x360=3040

Therefore, the first type of shipping fee is less, 2960 yuan.

1) 200 for drinking water and 120 for vegetables

Suppose car A x car and car B car y.

x+y=8,40x+20y>=200,10x+20y>=120 to get 4>=x>=2

then there is x=2, y=6; x=3,y=5;x=4 and y=4 are three schemes.

2) A 2x400+6x360=2960

2. 3x400+5x360=3000

3. 4x400+4x360=3040

The first type of shipping fee is less, 2960 yuan.

Known availability: drinking water: 200 pieces, vegetables: 120 pieces; (Equations can be obtained).

1) Set up a truck x and B truck y, which can be listed as an inequality group: 40x+20y>=200, 10x+20y>=120, known x+y=8, there are 4>=x>=2,6>=y>=4;There are three options;

2) Calculate the freight of the three schemes: 2 trucks A and 6 trucks B have the least freight, which is 2960 yuan.

1) Easy to obtain: 200 for drinking water and 120 for vegetables

Set up X cars for car A and car Y for car B.

x+y=8,40x+20y>=200,10x+20y>=120 to get 4>=x>=2

x=2,y=6; x=3,y=5;x=4 and y=4.

2) A 2x400+6x360=2960

2. 3x400+5x360=3000

3. 4x400+4x360=3040

so the first type of shipping is less, 2960 yuan.

Wait, wait, wait, wait for the other party's identity.

There is an ancient poem: I asked Li Sangong to open the store, all the guests came to this store, one room with seven guests and seven guests, one room with nine guests and one room empty, please ask how many guests and how many rooms. Think of this problem as an equation, how many rooms, how many guests?

Think of this question as an inequality problem, so how many rooms and how many guests?

A has two apples, and B has two more apples than A, find the number of apples of B.

(1) There is a question to obtain: drinking water 200, vegetables 120 assume car A x car, car B y car.

x+y=8,40x+20y>=200,10x+20y>=120 to get 4>=x>=2

x=2,y=6;

x=3,y=5;

x=4 and y=4.

2) One. 2x400+6x360=2960

2. 3x400+5x360=3000

3. 4x400+4x360=3040

Therefore, the first type of shipping fee is less, 2960 yuan.

1) 200 for drinking water and 120 for vegetables

Suppose car A x car and car B car y.

x+y=8,40x+20y>=200,10x+20y>=120 to get 4>=x>=2

then there is x=2, y=6;

x=3,y=5;

x=4,y=4

There are three options.

2) One. 2x400+6x360=2960

2. 3x400+5x360=3000

3. 4x400+4x360=3040

The first type of shipping fee is less, 2960 yuan.

A total of 38 students and 2 teachers from the first (1) class went on a spring outing in the suburbs. 1.Small boat, can sit 4 people, 35 yuan an hour.

2.The big boat can seat 6 people, 50 yuan an hour. They are going to return on the boat when they are going to take a small sail, so please ask which option is cheaper (or another allocation, such as 2 large and 3 small).

38 + 2 = 40 people.

1.Full boat 40 4 = 10

10*35=350 yuan.

2.All in a big boat.

7*50=350 yuan.

3.Solution: It is cheaper to rent 6 large boats and 1 small boat.

6 * 50 + 1 * 35 = 335 yuan.

Xiao Ming asked the math teacher how old he was this year. The teacher said, "When I was your age, you were just over 1 year old; When you reach my age, I'm just past the age of not being confused. "So how old is Xiao Ming? How old is the teacher? Do rotten and.

The year of confusion is 40 years old).

Solution: If Xiao Ming's current age is pure trace x, then the age difference between the two is: x-1, so the teacher's current age is: x+(x-1)=2x-1

When Xiao Ming reaches the age of the teacher, it will pass: x-1 years, and the age of the teacher at this time is: (2x-1) + (x-1).

So the column equation:

2x-1）+（x-1）=40

x=14 means that Xiao Ming is now 14 years old, and the teacher is: 2*14-1=27 years old.

The distance between station A and station B is 450 kilometers, with a slow train departing from station A traveling 65 kilometers per hour and an express train departing from station B traveling 85 kilometers per hour.

1) Two cars drive out at the same time, going in the opposite direction, how many hours after meeting (2) The fast car drives first for 30 minutes, the two cars go in the opposite direction, how many hours after the slow car travels The two cars meet (1): the speed of the slow + the speed of the fast = the total distance of 2 people.

Set to meet in x hours, according to the title. ”

65x + 85x = 450

150x = 450

x = 3 A: Met after 3 hours.

2): The speed of the slow person + the speed of the fast person = the total distance of 2 people.

Set how many hours the slow car travels and then the two cars meet.

65x +85x 450-1/2*85

In order to save energy, a unit charges a monthly electricity fee according to the following provisions: if the electricity consumption does not exceed 140 kWh, it will be charged at each kWh; If it exceeds 140 degrees, the excess part will be charged per degree. If the average electricity bill of an electricity user in April is $1/kWh, how much should the electricity user pay in April?

According to the statistics of the electric power department, 8 00 to 21 00 per day is the peak period of electricity consumption, referred to as "peak time", and 21 00 to 8 00 the next day is the trough period of electricity consumption, referred to as "valley time". In order to alleviate the contradiction of tight power supply demand, the city's electric power department plans to gradually replace the "peak and valley time-of-use" meters, and implement the new policy of "peak-valley time-of-use electricity price" for electricity, as shown in the following table

Time before changing the meter.

Peak time after meter change (8 00-21 00).

Valley time (21 00-8 00).

The price of electricity is yuan per kilowatt-hour.

per kilowatt-hour per kilowatt-hour.

Xiao Ming's family calculated the 95 kilowatt-hours of electricity initially used after the meter change, and it was calculated that it saved yuan compared with the 95 kilowatt-hours used before the meter change.

Exercise: A home appliance mall plans to buy 50 TVs from a manufacturer for 90,000 yuan. It is known that the manufacturer produces 3 different types of TVs, and the ex-factory prices are 1500 yuan per set for type A, 2100 yuan for type B, and 2500 yuan for type C.

1) If the home appliance mall purchases a total of 50 TVs of two different models at the same time, and costs 90,000 yuan, please study the purchase plan of the mall.

2) If the shopping mall can make a profit of 150 yuan from the sale of a type A TV, 200 yuan from the sale of a type B TV, and 250 yuan from the sale of a type C TV, which plan do you choose in order to make the most profit when selling two different models of TVs at the same time?

Lactating Xiaofang, Xiaohong goes to the park to play, and meets an abandoned baby on the side of the road. Because of the emergency situation at that time, the baby needed a total of 500ml of human milkWhen the two finished feeding, Xiaofang found that she had fed 100ml more milk than Xiaohong.

How much milk did Xiaofang and Xiaohong have for the baby?

Set: The purchase of goods** is x yuan.

90%x=100+（x-100）80%

90%x=80%x+20

10%x=20

x=200 to buy goods properly ** store A discount when it is less than 200, store B discount when it is greater than 200.

It is known that a clothing Bo Ying factory has 70 meters of cloth A and 51 meters of cloth in B, and plans to use these two fabrics to produce a total of 80 sets of two types of fashion, and it is known that a set of A model of fashion needs a kind of cloth rice, B cloth rice, and a profit of 45 yuan. To make a set of B model fashion, you need to use a kind of fabric rice, B kind of cloth rice, and you can get a profit of 50 yuan.

1) What are the options for the production of two types of fashion according to the requirements? Please design a song mold.

2) Which production scheme is based on the largest net profit and what is the maximum profit?