Set an x ton; B x-24 tons
(x-24- 12)*2=x+ 12
2x-72=x+ 12
x=84
84-24=60 tons -B
60+84= 144 tons
Arithmetic method:
Take out 12 tons of coal from pile A and put it into pile B, then the weight of the two piles of coal is equal;
It means that A is two more than B 12 tons.
After taking 12 tons from Party B to Party A, Party A has four more 12 tons than Party A, and Party A is twice as much as Party B,
48/(2- 1)=48 tons
Party A * * * is 2+ 1=3 copies.
48*3= 144 tons
2. When 40 students do three math problems, 25 students correctly answer the first question, 28 students correctly answer the second question and 3 1 student correctly answer the third question, then at least _ _ _ _ _ individuals correctly answer the third question.
This problem is a typical problem in mathematics-inclusion and exclusion. When encountering this kind of problem, it is usually solved by fan-shaped statistical chart.
1, now find out how many people didn't do it right. The first question: 40-25 = 15 (person)
2. Find out how many people didn't do the second question right: 40-28 = 12 (people) (because they say the least and do the most wrong).
3. How many people didn't answer the third question correctly: 40-3 1 = 9 (people)
40- 15-2 1-9 = 4 (person)
3. There are 282 books on shelves A and B. The number of books on shelf A is equal to that on shelf B. How many books are there on each shelf?
3/4 of the number of shelves A is equal to 5/9 of the number of shelves B. ..
It can be seen that A is B: (5/9)/(3/4)=20/27.
The sum of the two bookshelves is B: 1+20/27=47/27.
Therefore, b is: 282/(47/27)= 162 (Ben)
Answer: 282- 162= 120 (Ben)
4. Yuhong Primary School originally planned to plant apricot, peach and pear trees *** 1500. After planting trees, when 3/5 of the total apricot trees and 30 peach trees are planted, 15 pear trees will be temporarily transported. At this time, the number of the remaining three trees is just equal. How many trees were originally planned to be planted?
Suppose that "the number of trees in three kinds of trees is exactly equal", and each kind has X trees.
According to the meaning of the question, the apricot tree initially has x/40%, the peach tree initially has x+30, and the pear tree initially has x- 15, so:
x/40%+x+30+x- 15 = 1500
x=330
Original apricot tree: 330/40%=825 (plant)
The original peach tree is: 330+30=360 (tree)
The original pear tree is 330- 15=3 15 (tree)
There are 30 apricot trees, accounting for 3/5 of the total, and 15 pear trees are temporarily transported, and the other three trees are exactly the same.
According to this passage, in the original total, if apricot trees are 1, peach trees are (1-3/5)+30 and pear trees are (1-3/5)- 15.
If 30 peach trees are removed from the original total and 15 pear trees are added,
Then the total number becomes:1500-30+15 =1485 (tree).
This 1485 tree contains apricot 1, peach (2/5 of apricot) and pear (2/5 of apricot):1+2/5+2/5 = 9/5.
Known apricot tree is: 1485/(9/5)=825 (tree).
The original peach tree is: 825*( 1-3/5)+30=360 (tree).
The original pear tree is: 825 * (1-3/5)-15 = 315 (tree).
5. There are 200 students in grade five or six in a school. On Children's Day, there are 1 1 students in grade five, and 25% students in grade six go to the city to participate in the celebration. At this time, the remaining students in the two grades are equal. How many students are there in the sixth grade?
The remaining students in the sixth grade: 1-25%=75%, less than all the students in the fifth grade: 1 1.
That is, all the students in grade five are 1 1, which is 75% more than that in grade six.
If the number of students in grade five decreases by 1 1, which is 75% of that in grade six, then the total number is: 200-11=189.
Then there are: [200-11]/[1+75%] =108 students.