A math problem Primary 6 .

What is the maximum percentage of students in a class who subscribe to three kinds of publications, 80% of them subscribe to "Primary School", 75% subscribe to "Little", and 60% subscribe to "Youth"?

Analysis: The key to this question is to determine what the overlap of the three percentages is.

The first case: the class should subscribe to at least one copy. So make sure that 60 overlaps with 80, 100 80 20

60 20 40 (overlap).

No matter how 75 overlaps with it, the maximum is not more than 40

The second case: The class should subscribe to at least one copy. So make sure that 75 overlaps with 80, 100 80 20

75 20 55 (overlapping part) No matter how 60 is used to overlap it, the maximum is not more than 55

The third case: Some of the students in this class may have unbooked.

Then these three numbers overlap up to 60

Therefore, the answer to the third case meets the requirements of the question.

I've done this kind of math Olympiad, and I'm talking about the worst-case scenario at best, so it's not 60%, it's 15%.

Set: The maximum percentage of students who order all three books is x

Because the smallest of the three book subscription percentages is 60%, the number of people who subscribe to all three books must not exceed 60%.

Let's say the class is 100 people.

Subscriptions: 80 people.

Order "PHS": 75 people.

Youth: 60 people.

Because 80 and 75 and 60 can be duplicated at most, (60 will have 85 or 75 people?) )

So: 60 100 = 60%.

Set: The maximum percentage of students who order all three books is x

x=How many people are in the class!

Because the minimum number of "Teenagers" is 60%, if it is too large, the number of teenagers will not be enough.

60% 80% > 75% > 60% so take 60%.

The equation upstairs is wrong, because the classmate can also buy 2 books.

Simple: Fire: 16 2 15 = 120

Charcoal: 16 2 3 = 24 More Complex:

The total is: 16 2 30 = 240

Therefore, the fire burns: 240 15 30 = 120

Charcoal: 240 3 30 = 24

Analysis: The key to this question is to determine what the overlap of the three percentages is.

The first case: the class should subscribe to at least one copy. Then make sure that 60 overlaps with 80 and 60 20 40 (overlapping).

No matter how 75 overlaps with it, the maximum is not more than 40 In the second case: The class should subscribe to at least one copy. Then make sure that 75 overlaps with 80, and 75 20 55 (overlapping) no matter how 60 overlaps with it, the maximum is not more than 55

The third case: The students in this class can have some unbooked books, so the overlap of these three numbers is up to 60

Therefore, the answer to the third case meets the requirements of the question.

Actually, it's 60% because there are so many people in total, and if you exceed 60% then other people only book two, o(o...Simple, right.

Let me answer: 3 5 + 2 5 (1-20%)-=1 102 (1 10)=20 (block).

Xiaoyi: 20 * (3 5) + 2 = 14 (block).

Xiao Jiang: 20 * (2 5) (1-20%) = 10 (block) If you don't understand anything, just say it, if it's good, adopt it!

First remove the 2 pieces that Xiaoyi ate, and the rest have 24-2 22 pieces After Xiao Jiang also eats 20%, the ratio of the number of pieces between Xiaoyi and Xiao Jiang is 3 2, and the two of them have 3+2 5 servings and Xiao Jiang's 2 portions are left after eating the original 20%, and the number of servings when he doesn't eat 20% is 2 (1-20%) servings.

So after adding 20% of Xiao Jiang, the two have a total of 3+ servings (excluding the 2 pieces that Xiao Yi ate).

There are 22 pieces per serving.

So there were originally 4 pieces of Xiaojiang.

Xiaoyiyuan 4 3 + 2 14 pieces.

If you want to make a comprehensive formula, you have to use your own brain. (The last two lines of formulas above can only be single-columned, and cannot be listed in the comprehensive formula).

3 5 + 2 5 (1-20%) -=1 102 (1 10) = 20 (block).

Xiaoyi: 20 * (3 5) + 2 = 14 (block).

Xiao Jiang: 20*(2 5) (1-20%)=10 (block) choose me!!

Let Xiaojiang originally have x, then: Xiaojiang leftover (4 5) x, Xiaoyi leftover.

x+（6/5）x+2=24

x=10 has 14 pieces.

The distance of the first car.

The distance of car B.

So the speed of car B.

Set the speed of vehicle B x kilometers per hour.

Then there is: 650-(

Solve x = therefore, car B is speeding in kilometers per hour.

Hope it helps.

The speed of car B is x (kilometers per hour).

Solution x = kilometers per hour).

Relative speed of two cars: (650-200).

Therefore car B speed =

To sum up, there are 5 kings and 3 zhangs.

Master Wang processes x parts per hour on average, and Master Zhang processes Y parts per hour on average.

8x+6y=58

x=y+2 gives x=5y=3

Let the king be x per hour, and the system of equations for y will be solved x=5, y=3

So Master Wang has 5 per hour and Master Zhang has 3 per hour.

First, the largest fractional unit is (1 8), and the largest fractional value is (24 25) two, 7 15 (17 18-8 5 5 6) = 7 15 (17 18-4 3).

4. Replace 2 boxes of color with 8 boxes of white.

1500 RMB.

Set the original price x, the current price (

x=10000

Yuan) If the book has x pages, then 4 7 x + (4 5 x-13) = x

That is, the middle of the horizontal, * multiplied sign.

White x, color 4*x, then 6*x+2*(4*x)=350 i.e. 14x=350 to get x=25

Original price x, current price ( then, get x=10000

3500+(4350-3500)*(yuan).

If the book has x pages, then 4 7*x+(4 5*x-13)=x then (20 35+28 35)*x-13=x 13 35*x=13 then x=35

The largest fractional unit is one-eighth, and the largest fractional value is twenty-four-fifty-fifths.

2 out of 5 of a number is equal to 5 out of 8 of 320, find this number.

The canteen brought in 480kg of rice, which was 1/7 more than the flour brought inHow many kilograms of rice and flour did the canteen transport?

480 (1 1 7) 420 (kg).

420 480 900 (kg).

（1）320*5/8/=200

200 divided by 2 5 equals 500

A: This number is 500

A: A total of 900 kilograms of rice and flour were brought in from the canteen.

If there are x boys, then there are girls, and according to the question, the following equation can be obtained:

x-100=

The solution is x=320

So a total of 320+320* people participated.

The ratio of girls to boys is 1:4

1 for girls and 4 for boys, for a total of 5.

55% of the total number of people: 5x55% = portions).

Per serving: 100 (person).

A total of 80x5=400 (people) participated in this competition

The ratio of girls to boys is 1:4

Boys account for 4 (1 + 4) = 4 5 Total number of participants: 100 (4 5-55%) = 400 (person).

The method of using column equations:

Solution: If the number of boys participating in the competition is x, then the number of girls is 25%x, x=(x+25%x)*55%+100

The solution is x=320, 25%x=80, 320+80=400

A: A total of 400 people participated.

The number of boys is x, and the number of girls is y

From the meaning of the title, 55% (x+y)+100=x

y=25%x

The process is there, and the answer is your own.

The sixth grade of elementary school doesn't seem to have learned how to solve equations.