Problem solving: Primary 4 math problem .

2 41 = 82 kg.

1 35 = 35 kg.

35 + 82 = 117 kg.

117 3 = 39 kg.

1、a+b=200

b+c=150

a+c=160

The sum of the three formulas is 2*(a+b+c)=510, and the average of the three numbers =(a+b+c) 3=85

2. Female students x, the number of male students is 2x, and the average weight of the whole class = (x*35+2x*41) (x+2x)=39 kg.

1) Because when the sum of a+b, b+c, and a+c is added, a, b, and c all appear exactly twice, so 200 + 150 + 160 = 510 is twice the sum of these three numbers. So the sum of these three numbers is 510 2 = 255, then the average of these three numbers is 255 3 = 85.

Comprehensive solution: (200+150+160) 2 3=852) Assuming that there is 1 female student, then there are 1 2=2 male students. Then the total weight of the whole class is 41 2 + 35 1 = 117, so the average weight of the whole class is 117 (1+2) = 39 (kg).

Comprehensive solution: (41 2 + 35 1) (1 + 2) = 39 (kg).

1、a+b=200

b+c=150

a+c=160

2*(a+b+c)=510

a+b+c)/3=85

2. Female students x, male students 2x

x*35+2x*41) (x+2x)=39 kg.

a+b=200

b+c=150

a+c=160

The sum of the three formulas is 2*(a+b+c)=510, and the average of the three numbers =(a+b+c) 3=85

Set the female students as x, and the number of male students as 2x

The average weight of the whole class = (35x+2x*41) (x+2x)=117 3x=39 kg.

1. a=105 b=95 c=55

2.The number of female students is A, and the number of male students is B

2a=b, mean weight = (41b+35a) divided by (a+b) = (82a+35a) divided by 3a=39

a+b)+(a+c)+(b+c)=200+160+150=5102(a+b+c)=510 a+b+c=2553 average of numbers: 255 3=85

Assuming that there are 5 female students, then the classmates are 10 students, and the average weight of the class is (10*41+35*5) (10+5)=39 kg.

a+b=200

b+c=150

a+c=160

a=105b=95

c = 55 with an average of 85

2) The number of female students is A, and the number of male students is B

2a=b, mean weight = (41b+35a) divided by (a+b) = (82a+35a) divided by 3a=39

200 + 160 + 150) calculates two a, two b, two c, 2 calculates one a, one b, one c, 3 finds the average of three numbers.

There are 98 books in the library, 20 books were borrowed by the 4th grade, 10 books were borrowed by the 5th grade, and 12 books were returned, how many books are there in the library?

A total of 30 5 = 150 (kg) were taken out

Because the total weight left is equal to the original 2 boxes.

So take out 5-2=3 (box).

So each box weighs 150 3=20 (kg).

Since there are 2 boxes left, 3 boxes are taken out.

So, the weight of pears per box:

30 5 3 = 50 kg.

Take out 30 kg per box, a total of 5 boxes, indicating that a total of 30 * 5 = 150 kg is taken out.

After taking out 150 kg, the remaining pears are equal to the weight of the original two boxes of pears, indicating that the pears taken out are equal to the weight of 3 boxes of pears, so the weight of each box of pears: 150 (5-2) = 150 3 = 50 kg.

According to the question "30 kg is taken out of each box, and the total weight of the remaining pears in the 5 boxes is exactly equal to the weight of the original two pears", it is concluded that the 30 kg extracted from each of the 5 boxes, a total of 150 kg is just the weight of 3 boxes, so each box weighs 50 kg.

300 kg was transported from warehouse A and 2,700 kg was transported from warehouse B, and the weight of the remaining grain in the two warehouses was equal, so B was originally 2,700-300=2,400 kg more than A.

The grain storage silo in warehouse B is 4 times that of warehouse A, so the extra part is 4-1 = 3 times that of warehouse A, so A originally had 2400 3=800 kg.

B originally had 800 + 2400 = 3200 kg.

Solution: If A has x kilograms, then B has 4 kilograms.

x-300=4x-2700

x-4x=-2700+300

3x=-2400

x=2400/3

x=800, so B is 4*800=3200 (kg).

Answer: The original grain storage in granary A was 800 kilograms, and the original grain storage in granary B was 3,200 kilograms.

The original stock of a granary = (2700-300) 3 = 800kg

The original stock of B granary = 800 * 4 = 3200kg

1) 3840 pcs 960 pcs.

2) 560 bottles.

3) 28 games.

4) 2 hours.

5) Xiao Ling fast Xiao Ling.

I'll give you a list, you have to adopt, I'm fighting hard ==

1.2. 42+42÷23.Bottom: 144 2+8 Up: 144 2-8

If you want to add it, you will ask questions.

1.Meta).

2.42 2 + 42 = 63 (only).

3.Upper: 144 2-8 = 64 (Ben).

Lower layer: 144 2 + 8 = 80 (Ben).

4.(850-100) 3=250 (kg) 5(48-12) 9=4 (hours).

6.124 2 3 = 186 (cm).

7.1250 (25 5) = 10 (yuan) 8Meta).

A barrel of oil gross weighs kilograms, and the gross weight of half of the oil is kilograms, ask: how many kilograms does the barrel weigh?

kilogram) kilogram).

Principle: The gross weight of a barrel of oil includes the weight of the oil (called the "net weight") and the weight of the barrel. Gross weight after half of it is used.

No matter how much is used here, the weight of the barrel remains the same. In other words, the weight of the barrel in the gross weight at this time is the same as the weight of the barrel before use. Then the weight of the used part of the oil is the key.

The gross weight before use, and the gross weight after half of the oil is used is the weight of half of the oil used. Multiply this weight by 2 to get the weight of the whole oil. The net weight of all the oil is the weight of the barrel when you subtract the gross weight!

The unit price of the second time is (1500-1200*(1+20%)) 10=6, and the unit price of the first time is 6 (1+20%)=5

The first profit: 1200 5 * (7-5) = 480 yuan, the second profit is: 200 * (7-6) = 200, the loss is:

1500 6-200) * (6-7 * total profit: 480 + 200-160 = 520 yuan.

The questions in elementary school are so simple!

The unit price of the second time is (1500-1200*(1+20%)) 10=6, and the unit price of the first time is 6 (1+20%)=5

The first profit: 1200 5 * (7-5) = 480 yuan, the second profit is: 200 * (7-6) = 200, the loss is:

1500 6-200) * (6-7 * total profit: 480 + 200-160 = 520 yuan.

Earn 580 yuan, if the second price is also 7 yuan, this answer is right.

zhuan le

Solution: If the purchase price of the first book purchase is yuan, then the purchase price of the second book purchase is yuan According to the title:

Solution: It is tested to be the solution of the original equation.

So the first time I bought a book, it was (this book).

The second purchase of the book is (this book).

The first time you make money is (yuan).

The second time to make money is (yuan).

So two times a total of money (yuan).

Answer: The boss made a lot of money by selling books twice, and he made a total of 520 yuan

Make money, earn 520 yuan.

The cost price is 5 yuan for the first time.

$6 for the second time.