Primary school students examine questions and train their thinking.The following are some examples of the answers to some primary school students 'questions:
** 1. Numeric Patterns **
1. Fill in the blanks according to the rules, such as 10, 7, 4 ().
- The idea was to observe the difference between the numbers. 10 - 7 = 3, 7 - 4 = 3. The rule was that the latter number was 3 less than the previous number, so the number in the parenthesis should be 1.
** 2. Numeric Operations **
1. One and one forty-second plus two and one fifty-sixth plus three and one seventy-second.
- The idea was to first add the whole numbers 1, 2, and 3 together to get 6. For the fraction part, 1/42 could be converted into 1/6 minus 1/7, 1/56 could be converted into 1/7 minus 1/8, and 1/72 could be converted into 1/8 minus 1/9. After adding up, the intermediate scores could be eliminated, and the final result was 1/6 minus 1/9. The general score was calculated as 3/18 minus 2/18, which was 1/18. The final result was 6 and 1/18.
** 3. Numeric Puzzles **
1. For example, a circle, a five-pointed star, and a triangle would add up to 888.
- [Thinking: If we first solve the numbers represented by each graph according to the conventional thinking, the process will be more complicated.] However, if the three numbers were the same, they could divide 888 by 3 to get 296. That meant that the number represented by each figure was 296.
** 4. Practical-use category **
1. Xiao Ming was seven years old this year. His mother was 21 years older than him, and his father was five times his age.
- Mother's age: 7+21 = 28 (years old).
- [Father's age: 7×5 = 35 (years).]
2. There were 28 girls in Class 2 (3), and 12 fewer boys than girls.
- [Number of male students: 28 - 12 = 16 (people)]
- Total number of male and female students: 28+16 = 44 (people).
3. The students planted 25 trees in the morning, 19 in the afternoon, and 38 yesterday.
- The total number of trees planted today was 25+19 = 44 trees.
- The number of trees that grew more today than yesterday: 44 - 38 = 6 (trees).
4. Chang 'an First Primary School originally had 39 male teachers and 25 female teachers. Eight of them were transferred away.
- [Total number of teachers: 39+25 = 64 (people)]
- [Current number of teachers: 64 - 8 = 56 (people).]
5. There were eight willow trees planted in the front, back, left, and right of the flower bed.
- Because trees were planted in all four directions, four trees (trees with four corners) would be counted repeatedly, so the total number was 8×4 - 4 = 28 (trees).
6. There were three small cars, one large bus, and one large bus.
- The total number of people that could sit was 3×4+25 = 12 + 25 = 37 (people).
7. Xiao Hong read a book with 90 pages. On average, she read eight pages a day for nine days.
- [Number of pages seen: 8×9 = 72 (pages)]
- [Remaining pages: 90 - 72 = 18 (pages)]
8. Xiao Hua had five bags of sugar, each bag had six grains, and there were three more grains.
- The total amount of sugar: 5×6+3 = 30+3 = 33 (grains).
9. There were 25 boys, 21 girls, and two teachers.
- Total number of people: 25+21+2 = 48 (people). Since 48<50, a 50-seat car was enough.
10. There were ten floors in a certain building, and each floor was four meters tall. Xiaoming stood on the balcony of the eighth floor.
- The distance between Little Ming and the ground was the height of a seven-story building, which was 7×4 = 28 meters.
11. There were six small snails, but there were three times as many ants as it was.
- [Number of ants: 6×3 - 2 = 18 - 2 = 16]
12. There were 36 boxes of pears and 37 boxes of apples. The small truck could transport 70 boxes at a time.
- The total number of boxes of pears and apples: 36+37 = 73 (boxes). Because 73>70, they could not be shipped all at once.
13. A large towel was 38 yuan and the salesperson was 50 yuan.
- The amount of money to be changed: 50 - 38 = 12 yuan.
14. Xiao Hong's family bought a box of Red Fuji and ate 18 of them. There were six left.
- The original number of Red Fujis in a box was 18+6 = 24.
15. The teacher assigned 80 mental calculations, and Xiaoxin did 69.
- Roughly, 80 - 69 = 80 - 70 = 10 paths.
16. There were five Chinese books on the table. One book had ten pages, and one math book had twenty-four pages.
- The number of pages in the five language books was 5×10 = 50 (pages).
- The total number of pages in the five language books and one math book was 50+24 = 74 (pages).
17. Xiao Ming picked six types of flowers, seven of each type. Xiao Hua picked four types of flowers, eight of each type.
- [The total number of flowers Little Ming picked: 6×7 = 42 (flowers).]
- The total number of flowers picked by the small flowers: 4×8 = 32 (flowers).
- The total number of flowers picked by the two was 42+32 = 74 (flowers).
18. There were two desks in her mother's office. One of them had four books of each of nine different kinds, and the other had eight books of each of three different kinds.
- [Total number of books on the first desk: 9×4 = 36 (books)]
- [Total number of books on the second desk: 3×8 = 24 (books)]
- The total number of books on the two desks was 36+24 = 60 (books).
19. Xiaoming saves 4 yuan every month. The amount of money that can coexist for half a year (6 months) is 4×6 = 24 yuan.
20. There were two vases, one with six flowers and the other with four flowers.
- The total number of flowers in the two vases was 6+4 = 10 (flowers).
21. There were two rows of poplar trees on the school field, with six trees in each row.
- [Total number of poplar trees: 2×6 = 12 (trees)]
22. Each brush was 3 yuan, and Xiao Hong bought 4 of them.
- Total amount of money used: 3×4 = 12 yuan.
23. A table had four legs, and the total number of eight table legs was 4×8 = 32 (legs).
24. Little Red bought some glass beads and put them in a bag of five. There were three bags in total, and there were two left.
- [Total number of glass orbs: 5×3+2 = 15+2 = 17 (pieces)]
25. A triangular piece of paper had three corners, and the total number of corners of six triangular pieces of paper was 3×6 = 18.
26. A cube had six faces, and each face had four corners.
- The total number of horns: 6×4 = 24.
27. Xiao Hong had 28 pictures, and Xiao Ming had 16 more.
- [Number of Little Ming's pictures: 28+16 = 44 (pictures)]
28. Class 2 (3) bought 62 storybooks and 38 science books.
- The number of storybooks that outnumbered science and technology books: 62 - 38 = 24 (books).
29. The store sold 81 sets of clothing on the first day and sold 18 sets less on the second day.
- The number of sets sold the next day: 81 - 18 = 63 sets.
30. There were three students in the classroom, and nine boys and nine girls came in.
- The total number of students now was 3+9+9 = 21.
31. To make a shirt, he had to sew five buttons on the front and two buttons on each cuff.
- The total number of buttons to be sewn: 5+2×2 = 5+4 = 9 (pieces).
32. A short rope was six meters long, and a long rope was three times longer than the short rope.
- The length of the rope was 6×3 = 18 meters.
33. There were eight times as many boxes of ballpoint pens as pencil boxes in the shop, with seven boxes of pens.
- [Number of boxes of ballpoint pens: 7×8 = 56 boxes]
34. There were 22 wild geese, 9 fewer geese and 19 more ducks.
- [Number of geese: 22 - 9 = 13]
- [Number of ducks: 22+19 = 41]
35. Ming Ming, Lan Lan, and Le Le watered the saplings on campus. On average, each person watered six saplings.
- The total number of trees watered was 3×6 = 18 (trees).
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