Mathematics classic questions of grade six in primary school Help, please!

Mathematics classic questions of grade six in primary school Help, please!

1. The students of team a and team B set out from two places 18km apart at the same time and walk towards each other. A student rode at the speed of 14km / h to contact between the two teams. Team a was 5km / h and team B was 4km / h. When the two teams met, how many kilometers did the students ride?
1. 18 / (5 + 4) = 2 hours
2. Arrange the five numbers from small to large, the average number is 38, the average number of the first three numbers is 27, the average number of the last three numbers is 48, what is the middle number?
2) 5, 190 in total
Sum of the first two numbers 190-48 * 3 = 46
If the third number is x, then: (46 + x) / 3 = 27
X=35
3. Find out the greatest common factor of 469 and 1072 by division
3. 1072 / 469 = 2-134
469 / 134 = 3:67
134 / 67 = 2 more than 0
That is, the greatest common factor of 469 and 1072 is 67
4. The numbers in () x () = 1995? () are different
4、1995=3*5*7*19=21*95=35*57
The numbers in () are different
So fill in (2) (1) x (9) (5) = 1995
Or (9) (5) x (2) (1) = 1995
All three children grow trees in their homes. Xiaoyue says that our family has 20 fewer trees than Xiaohua's. Xiaoliang says that our family has one fourth more trees than Xiaoyue's. Xiaohua says that our family has one fifth more trees than Xiaoyue's,
Q5. How many trees have Xiaohua planted
5.120 trees
6. How many trees have Xiaoliang planted
125 trees
7. How many students can be informed by a four minute phone call?
Four minute maximum notice: one in one minute, three in two minutes, seven in three minutes and fifteen in four minutes
How many minutes does it take to inform 60 students?
Six minutes
9. The answer to math question 90100600,3 is 2400 (calculated by addition, subtraction, multiplication and division or brackets) 90 △ 3 × 100-600 = 2400
10. There is another question. My sister takes 48 minutes more than her sister to do math and 42 minutes more than her sister to do English. My sister takes 44 minutes to do math and English. How many minutes does my sister take to do English practice?
Let my sister do math with X, English with Y 1, {x + y = 44 {x = 25}
Answer: it took 19 minutes
Answers to sixth grade Mathematical Olympiad questions
What was the number of boys and girls in the school
There are story books in the library. After 40% of the story books are lent out, 360 are bought. At this time, the ratio of story books to the original is 3:4. How many are there?
1. The original 4:3 (male vs. female) is now 6:5 (male vs. female) boys are unchanged. Try to integrate the ratio
4: 3 = 4 × 1.5:3 × 1.5 = 6:4.5
Now 6:5 (male vs. female) 6:4.5 (male vs. female) 2 (5-4.5) = one share = 4 (person)
A total of 6 + 4.5 = 10.5 (shares) 4 × 10.5 = 42 (persons)
2. Let X be (1-40%) x + 360 = the number of books now
It's three now, it turned out to be four
（1-40％）x+360 = x÷4×3
60％x+360 = x÷4×3
Three fifths x + 360 = x × three fourths
x = 2400
The second method: lending 40% = there are 60% story books left. The price difference between the story books and the original story books is 3:4. Now the price difference between the story books and the original story books is 3:1, which is divided into four parts, that is, 75%: 25%. 40% is the lending rate, 25% is the price difference between the story books and the original story books, and 40% - 25% is the corresponding score of 360 books, which is 15%
Specific quantity (360) △ corresponding score (15%) = Unit "1" (original quantity)
stick out a mile:
360 △ 15% = 360 × 100 / 15 = 360 × 20 / 3 = 120 × 20 = 2400