① The circumference of a rectangle is 2C. If its length is a, then its width is? ② If there are three consecutive integers, and N is used to represent the middle one, then the other two are? ③ Buy unit price m yuan notebook n, pay 30 yuan, should find? When answering, write down the steps of calculation. If you have a concept, say it~

① The circumference of a rectangle is 2C. If its length is a, then its width is? ② If there are three consecutive integers, and N is used to represent the middle one, then the other two are? ③ Buy unit price m yuan notebook n, pay 30 yuan, should find? When answering, write down the steps of calculation. If you have a concept, say it~

1、
Width x
Then 2 (a + x) = 2C
a+x=c
x=c-a
Width C-A
2、
The difference between consecutive integers is 1
So it's n-1 and N + 1
3、
It's Mn yuan altogether
Find 30 mN yuan

According to the market survey, a household appliance manufacturer decided to produce air conditioners, color TV sets and refrigerators every week (120 working hours)
According to the table below, the name of household appliances is air conditioner, color TV and refrigerator
Working hours 1 / 2 1 / 3 1 / 4
Output value (ten thousand yuan / set) 0.40.30.2 man hours required. According to the above information, how many color TV sets and air conditioners are produced each week, just making the total output value reach 980000 yuan?

There are x air conditioners and Y color TV sets
x*1/2+y*1/3+60*1/4=120
x*0.4+y*0.3+60*0.2=98
By solving the equation, x = 170 air conditioners and y = 60 color TV sets are obtained

Mathematical problems of algebra in the second year of junior high school
If (2008-A) (2010-a) = 2009, then the value of (2008-A) (2008-A) + (2010-a) (2010-a)

(2008-a)(2010-a)=2009(2009-1-a)(2009+1-a)=2009(2009-a)^2-1=2009(2009-a)^2=2010(2008-a)(2008-a)+(2010-a)(2010-a)=(2009-1-a)(2009-1-a)+(2009+1-a)(2009+1-a)=(2009-a)^2-2(2009-a)+1+(2009-a)^2+2(2009-a)+1=...

The number of color TV sets in supermarkets is 90 less than that in refrigerators, and the number of refrigerators is 2.5 times more than that of color TV sets. How many are the two kinds of home appliances

Color TV (90-18) / (2.5-1) = 72 / 1.5 = 48 sets
Refrigerator 48 + 90 = 138 sets

Primary school sixth grade mathematics problems online and so on! Hurry! Hurry! Hurry!
It's 21.1km around the lake. Xiaoming and Xiaohua walk back from the same place by the lake. Xiaoming walks at the speed of 4.6km per hour and takes a rest for 5 minutes after every hour. Xiaohua takes a rest for 10 minutes after every 50 minutes at the speed of 5.4km per hour. How many hours do they meet after they set out?

2 hours and 10 minutes later
4.6 * 2 + 5.4 * 110 / 60 = 19.1
21.1-19.1=2
2 / 10 * 60 = 12 points
2 hours and 22 minutes in total

In the activity of "home appliances to the countryside", a factory has to transport 100 washing machines to neighboring towns. There are 4 A-type trucks and 8 B-type trucks available. The transportation cost of each A-type truck is 400 yuan, which can hold 20 washing machines; the transportation cost of each B-type truck is 300 yuan, which can hold 10 washing machines
A. 2000 yuan B. 2200 yuan C. 2400 yuan D. 2800 yuan

Let X type a freight cars and Y type B freight cars be used, and the transportation cost is Z yuan. According to the meaning of the problem, the linear constraint condition 20x + 10Y ≥ 1000 ≤ x ≤ 40 ≤ y ≤ 8 is obtained, and the minimum value of the linear objective function z = 400X + 300y is obtained. When x = 4Y = 2, Zmin = 2200

There are five consecutive natural numbers. The third number is three times more than two fifths of the sum of the first and fifth numbers. What is the smallest number?
Writing is arithmetic,

n-3=0.4(n-2+n+2)
have to
n=15
13\14\15\16\17

If the average price of home appliances sold is: 1500 yuan for each color TV set, 2000 yuan for each refrigerator, 800 yuan for each mobile phone, and the number of refrigerators (including freezers) sold all the time
Its total sales of 3.5 million units (units), to 13% of the subsidy, using the equation to solve the unknown!

The number of color TV sets sold is x, the number of refrigerators sold is 1.5x, and the number of mobile phones sold is (350-2.5x)
0.15x + 0.2 * 1.5x + 0.08 * (350-2.5x) = 500000 yuan
0.45x+28-0.2x=50
0.25x=22
The number of color TV sets x = 880000,
The number of refrigerators is 1.5x = 1.32 million
The number of mobile phones sold is (350-2.5x) = 1.3 million
Government subsidies for color TV = 880000 * 0.15 * 13% = 171.6 million yuan
Government subsidized refrigerators = 1.32 million units * 0.2 * 13% = 343.2 million yuan
Government subsidized mobile phones = 1.3 million * 0.08 * 13% = 135.2 million yuan

[urgent request] sixth grade math problem
It took a car two hours to complete four fifths of the journey. At this speed, it takes () hours to complete the journey

You need to:
1/(4/5/2)
=1/2/5
=5/2
=2.5 hours

One hundred refrigerators from the home appliance supermarket are sold at 1500 yuan each. Each refrigerator sold can get 20% profit from the selling price. Because three of them are damaged, they are sold according to the price
How much is the actual profit after these refrigerators are sold out?

1. 20% profit from 97 refrigerators → 97x1500x20% = 29100
2. Because 1500 is the selling price and 20% is the profit, the cost of 1500-1500x20% = 1200
3. 3 Taian is sold at a 10% discount, 1500x0.9 = 1350; Profit: (1350-1200) X3 = 450
4. So the total profit is 29100 + 450 = 29550