1, 18/(5+4)=2 hours
2. Arrange the five numbers from small to large, the average is 38, the average of the first three numbers is 27, the average of the last three numbers is 48, and what is the middle number?
2) The quantity is 5 *** 190.
The sum of the first two numbers is 190-48*3=46.
If the third number is x, then: (46+X)/3=27.
X=35
3. Find the greatest common factor of 469 and 1072 by division.
3. 1072/469=2 and 134
469/ 134=3+67
134/67=2+0
That is, the greatest common divisor of 469 and 1072 is 67.
4.()()x()()= 1995？ The numbers in () are different.
4、 1995=3*5*7* 19=2 1*95=35*57
The numbers in () are different again.
So fill in (2) (1) x (9) (5) =1995.
Or (9) (5) x (2) (1) =1995.
All three children are planting trees at home. Xiaoyue said that my family planted 20 fewer trees than Xiaohua's. Liang Xiao said that there are more kinds of trees in my house than in Xiaoyue's 1/4 trees. Xiaohua said that there are more kinds of trees in my home than in Xiaoyue's 1/5 trees.
Q 5。 How many trees has Xiaohua planted?
5. 120 trees
6. How many trees have been planted in Liang Xiao?
6. 125 trees
7. How many students can I call in four minutes?
Four minutes maximum notice: one minute 1, two minutes 3, three minutes 7, four minutes 15.
How many minutes does it take to inform 60 students?
Six minutes
9 The answer to the math problem is 90, 100,600, 3 is 2400 (calculated by addition, subtraction, multiplication, division or brackets) 90÷3× 100-600 =2400.
10. One more question. It takes 48 minutes for my sister to do English questions, 42 minutes for her sister to do English questions, and 44 minutes for her sister to do math and English. So how many minutes did her sister practice English?
X is used in mathematics and Y 1 in English, {X+Y = 44 {X = 25.
{x+42=y+48 solution {y= 19 a: it took 19 minutes.
The answer to the sixth grade Olympic math problem
The original ratio of boys to girls in the school was 4: 3, and later it was transferred to two girls. Now, girls are 5/6 of boys. How many boys and girls are there? (First question)
There are story books in the library. After 40% of the story books were lent out, 360 were bought. At this time, the ratio of story book to original work is 3: 4. How many books are there?
1. The original ratio was 4:3 (male to female ratio), but now it is 6:5 (male to female ratio). So do boys. Try to unify the proportions.
4: 3 = 4×1.5: 3×1.5 = 6: 4.5 (originally male to female)
Now 6:5 (male to female) 6:4.5 (male to female) 2÷(5-4.5)= one copy =4 (person)
* * * There are 6+4.5= 10.5 (copies) and 4× 10.5=42 (people).
2. Suppose it is x. (1-40%) x+360 = the number of books now.
There are three now, and there used to be four.
( 1-40%)x+360 = x÷4×3
60%x+360 = x÷4×3
3/5 x+360 = x× 3/4 (score cannot be entered)
x = 2400
The second method: lend 40%= 60% storybook 3: 4, and the difference between the current storybook and the original storybook is 3: 1, which is divided into four parts, that is, 75%: 25%. 40% is the borrowing rate, 25% is the difference between the storybook and the original storybook, and 40%-25% is the corresponding rate of 360 books. 15%.
Specific quantity (360)÷ corresponding score (15%)= unit "1" (original quantity)
Be clear at a glance:
360 ÷15% = 360×105 = 360× 20 =120× 20 = 2400 (Ben)