Math problems will not be done, detailed process, plus points

One. Analysis: (1) The rice bought by Xiao Ming's family is not discounted, so it must not exceed 180kg, and if you add another 40kg, it will be discounted, then it must exceed 140kg (180-40=140kg).

Solution: (1) 140 x 180 is obtained from the equation that can be listed

That is, the amount of rice that Xiao Ming's family originally planned to buy was 140 x 180

Analysis: (2) The key descriptor is: the original price of 4kg is the same as the purchase of 5kg at a discounted price, and the corresponding equivalent relationship is: original price of kilograms: discounted kilograms = 4:5

Solution: (2) According to the meaning of the question, x (x+40)=4 5 is obtained from the corresponding proportion

x=160

A: Xiao Ming's family originally planned to buy 160 kilograms of rice

Supplement: The condition of not enough discount, indicating that it is less than 180 kg, and adding 40 kg is enough to discount, taking 180 as the standard, indicating that it exceeds 140 kg The key descriptor needs to be found first

Two. Team A completed one-third of the total work in 1 month alone, and it can be known that the construction speed of Team A is 1 3 per month. At this time, the remaining total engineering quantity is 1-1 3 = 2 3 of the total project, which is completed by A and B working together for half a month, then the workload completed by A in this half month is 1 3 2 = 1 6 of the total project, then the remaining engineering quantity is completed by B, that is, the medium engineering quantity (2 3-1 6 = 3 6 = 1 2) (the remaining engineering quantity - the engineering quantity done by A in this half month = the engineering quantity done by B in this half month), it can be seen that A has done 1 6 of the total project in this half month, and B has done 1 of the total project in this half month 2, so the construction speed of team B is fast.

Team B's construction is fast.

First, you need to set out the original price of Y yuan per kilogram of rice

Then xy=500 x(y+40)·80%=500xy=500 (xy+40y)·80%=500 bring xy=500 into the following equation 500+40y)·80%=500 can be solved y= x=160

Second, analyze the total amount of work is x

Then Team A completes the construction alone in one month x 3, leaving 2x 3 and the two teams A and B work together to complete it in half a month, and this half month A completes x 3 and divides it by 2 to x 6

x-x 3-x 6=x 2 That is to say, this x 2 was completed by Team B in another half a month

So it only takes 1 month for Team B to complete it alone, and it takes 3 months for Team A to complete it alone, so Team B is fast.

The landlord has extra points

Thank you, typing is not easy

The second question is B fast.

A completes one-third in a month, and if the speed remains the same, the next half a month will complete one-half times one-third, that is, one-sixth, and A completes a total of one-third plus one-sixth, that is, one-half, then B also completes one-half, so B's speed is half a month to complete one-half, and A completes one-sixth in half a month, so B is fast.

Question 1: Are there any fewer conditions? So there are a number of problems, such as; What is the unit price of rice? Hit the discount? Originally the quantity to buy?

How much to buy now?

The fifth term in the sequence is a5=(-1) (5+1) (15-2).

The 100th term in the sequence is a100=(-1) (100+1) (300-2).

Let half of the waist be x and the bottom be y ( then the midline of a waist divides the triangle into two parts; A waist length 2x + half of the waist length x half of the waist length x + bottom y).

If the length of the part is 18, then the column formula 3x=18 then x=6 and because the length of the part is 14, the columnar formula x+y=14, y=8 and the three sides are 12, 12, 8

If the length of the part is 14, then the column formula 3x=14 then x=14 3 and because the length of the part is 18, the columnar formula x+y=18, y=40 3 3 is 28 3, 28 3, 40 3 on three sides

Let the bottom edge be x and the waist be y

Then the two segments are x+y 2 and x+x 2 = 3x 2 if x+y 2 = 18

3x/2=14

then x=28 3

y=36-2x=52/3

If x+y 2=14

3x/2=18

then x=12y=28-2x=4

The sum of the two sides of the triangle is greater than the third side.

So y+y>x

4+4>12, not true.

So the trilateral length is 28 3, 52 3, 52 3

Step 1: 1400 kg of potion and 500 kg of farming, that is, water is 1400-500 = 900 kg.

2: Divide 900 grams of water by the water to be mixed with pesticides of A and B per kilogram (20 + 40), that is, 900 divided by (20 + 40) = 15 kg.

Three: The ratio of A: B is 2:1, then A pesticide is 15 times 2 = 30 kg B pesticide is 500-30 = 470 kg.

To dispense 1400 kg of potion should be 14000 kg, assuming that X kg is needed for a pesticide A, 500-x kg is needed for a pesticide B, 20x+40(500-x) = 1400020x = 6000

x = 300 kg.

Solution: Set the need for pesticide A x kg, and the need for pesticide B y kg. Equation: x+y=500 20x+40y=1400 x=300 y=200 The answer requires 300 kg of A and 200 kg of B.

If the first drug is x kg, then the second drug is (500-x) kg x + 20x + (500-x) + (500-x) 40 = 1400x + 20x + 500-x + 2000-40x = 14002500-20x = 1400

20x=2500-1400

x=1100÷20

x = 55 kg.

Type B: 500 55 445 kg.

There is something wrong with your data, please check it? Here's how it works.

Set X kg for Type A and 500-x kg for Type B.

Type A water: 20x

Water use for type B: 40 (500-x).

Two kinds of water in common: 1400-500 = 900 kg 20x + 40 (500-x) = 900

2x+4(500-x)=90

One, (1)2+, (2)2+ solution x=8

Second, type A: 2190 + 3650 * yuan.

B: 2190 * yuan, that is, it is not cost-effective to buy type A.

Set at least x fold, 2190x 10 + 3650 * solution x = 8, that is, at least eight fold is cost-effective.

Three, (1) 48-a-(2a+3)-(a+2a+3)=42-6a2) can not get the key finger, is a long line segment of 24cm.

3), the third or fourth side is the largest, from 2 (a + 2 a + 3) greater than 42-a, a is greater than 3; Or from 42-6a+a+2a+3 greater than a+2a+3 to get a less than 8, that is, a is greater than 3cm, and the small draft slips to 8cm

It's hard to type.,I'm going to tell the teacher to listen.。。。

1.(85*11+x) 12= solution x=913(36+2*21+36)/2*22=1254y=45

y=207.High Lego 50*7 (20+1) = Milk 8(12-2) 2=5cm or (12+2) 2=7cm, n=7+11+13=31

11.（2y+396）/26=（2y+252）/18 y=36

13.(y-99)*3+90*2+9=1989 y=69916

1.There are 12 people in a group, a math test, Xiao Wang was sick and did not come, the average score of the rest of the students was 85 points, after Xiao Wang made up the exam, his score was higher than the average score of 12 people, how many points did he take?

11 times 85 = 935 Let the Xiao Wang score be x (x+935) divided by 12+

x\12+935\12+

x+935+66=12x

11x=-1001

x = 91 Xiao Wang scored 91 points.

2.An internal transmission line can supply power to up to 3 air conditioners at the same time, and a company installs 1 air conditioner in each of 4 offices, and each room can use air conditioners for several hours a day?

Air conditioning is available in each room for x hours.

4 times x = 3 times 24

4x=72x=72\4

x=183.A theater has 22 rows of seats, the first row has 36 seats, and the back row has 2 more seats than his previous row, how many seats does this theater have?

Multiply by 22 2

42+36+36]x11

114x11

4.What is the fraction of a fraction of the numerator plus 2 can be reduced to three-quarters, and the denominator plus 2 can be reduced to one-half?

Let the numerator of this fraction be x and the denominator y y

x+2)\y=3\4 x\(y+2)=1\2

x = 1 2 multiplied by (y + 2) = (1 2) y + 1 is brought into the equation.

y=3\4(1\2)y+3】\y=3\4 x=(1\2)x12+1

1\2)y+3]x4=3y x=6+1

2y+12=3y x=7

y= -12

y=12 This score is 7 12

1. Let Xiao Wang X points, then by the condition: x=(, solve x.

2. 24 hours * 3 air conditioners = 72 hours, 72 hours 4 air conditioners = 18 hours. 18 hours a day.

3. Use the difference series, let n=22, the first term a1=36, the tolerance d=2, the first n term sum = n*a1+1 2(n*n+n)*d, which is the number of seats.

4. Let the fraction be x y, and the condition is (x+2) y=3 4, x (y+2)=1 2, and the inequality group is solved.

5. Set up x people in the class, x*

6. If x days are in, then there are 2x+20=3x.

It's not so much, I really won't come out with a few questions, I'll help you.

Hell, isn't that the question of our math contest, half of which is the question of our math contest!

The air conditioning can work for 18 hours.

丨a丨=4,a= 4;

丨b丨=3,b= 3;

Because a>b

So a can only take 4 and b equals 3