Mathematical problem 1 of reverse thinking
1. Xiaohong reads a book. She has read 136, and there are 89 pages left. How many pages are there in this book?
2. Students go for an outing. There are 97 students in Grade One and 0/05 students in Grade Two. There are as many students in Grade Three as in Grade One. How many students are in Grade Three?
3. A pile of bricks. On the first day, 275 yuan was used to build a house for a puppy, and on the second day, 225 yuan was used to build a house for a chicken, leaving 300 yuan. How many bricks are missing from this pile? How many bricks are there in this pile?
4. Mercury: It takes me 88 days to go around the sun. Mars: It takes me 687 days to go around the sun. Earth: The number of days I go around the sun is 465,438+00 days less than your total. How many days does it take for the earth to go around the sun?
5. A bundle of wires is 1000m long and needs 700m m.. How much more rice is left than used?
6. Xiaohong: There are 35 trees in each row. Xiao Ming: Now the second row is watered, and 10 trees are watered to the end. How many trees have we watered?
7. There is a string of beads, press? Three black and two white? Arrange. Think about it (pictured). Is the number 28 bead black or white? Where's the 40th? ●●●○○●●●○○●●●○○。 .。 . . .
8. Students in Class 2 (4) go to plant trees. If there are 8 trees for each race, there will be 2 more trees. If there are 9 trees for each race, there will be 5 fewer trees. There are () saplings in this batch.
9. Bread costs 80 cents each. How many slices of bread can 5 yuan buy? How much is left?
10, the dance team has 46 people, the chorus is less than the dance team 15, and the instrumental band is 2 1 more than the chorus. How many people are there in the chorus and the instrumental band respectively?
1 1. There are 92 peach trees, 18 pear trees are more than peach trees, 18 apple trees are less than peach trees. How many pear and apple trees are there?
12, a teapot 50 yuan, a teacup 15 yuan. Teacher Wang bought a teapot and six teacups and paid 150 yuan. How much should he get back?
13. Xiao Pang tied a balloon, and seven balloons were tied into a bundle. After tying 8 bundles, there are still some balloons left, but not enough to tie one bundle. There are at most () balloons left and at least () balloons left.
14. Divide a plane into several parts with straight lines. Five lines can divide the plane into () parts at most.
15. Four numbers (1, 2, 3, 4) can form two digits of (), and there are no duplicates.
16.20 12 June 1 is a Friday, and the 40th day from this date is a week ().
17. There is a rope. The first time, half of it was cut more than one meter, and the second time, the remaining half was cut less than one meter. There are still 3 meters left. This rope used to be () meters long.
18. If the rope shown below is straightened, its length is about () cm, leaving 3 meters. This rope was originally () meters.
19. On one side of a bridge, 10 billboards are erected from the bridge head to the end of the bridge. There are five colorful flags between every two billboards, and there are () colorful flags on this bridge.
20. Some people want to work on the 8th floor, but the power is out. If it takes 14 seconds to walk from the 6th floor to the 3rd floor, it takes () seconds to walk to the 8th floor at the same speed.
Mathematical problems of reverse thinking II
2 1. Schools should plant colored flags on both sides of the playground aisle, each side is 10 meter long, and one colored flag should be inserted every 2 meters. The beginning and end of the aisle should be inserted, and one side should be inserted.
22. My uncle has a triangular flower bed with 5 plants on each side, * * 12 plants. How to plant it? Please draw a picture.
23. Xiaohong's family has a quadrangular flower bed with 6 pots of flowers and 22 pots on each side. How to put it? Please draw a picture.
24. On one side of a road, nine trees were planted from beginning to end, and the distance between every two trees was 2 meters. This road is () meters long.
25. A rope, folded in half twice, cut a knife every certain length, * * * cut three knives, and the original rope was cut into () sections.
26. In Formula 63-7? 7, should first calculate (), and then calculate (). In formula 8 1 (18-9), you should calculate () first and then ().
27. Fill in the number after finding the rule.
( 1)408、409、( ) 、( )、( )
(2)90、87、84、( )、( )、( )
(3)325、330、335、( )、( )、( )
(4)( )、( )450、500、550
(5)( )3027、3067、( )、( )、( )
(6)4896、4776、4656、( )、( )、( )
28. What can I fill in ()?
( )? 7 & lt40 43 >； 7? ( ) ( )? 9 & lt60 5? ()& lt26 27 >； ( )? 8 6? ()< 56 years old
29. A four-digit number. Starting from the right, the number in the first place is 8, the number in the third place is 7 larger than the number in the second place, the number in the first place is 4 times that in the second place, and the sum of any three adjacent numbers is 19. This number is ().
30. Think, calculate and fill in.
( 1)87-8-8-8-8-8-8-8-8-8-8=( )
(2)30? 7=( )( )
(3) 145+27+ 155+373=( )
(4) 1+2+3+4+5+6+7+8+9=( )
3 1. In the evening, Xiaoya was doing his homework when the power went out suddenly. Xiaoya pulled the switch twice, and when her mother came back, she pulled it again in Xiaoya's room ().
32. Before New Year's Day, students give each other New Year cards. If everyone receives a card and sends it back, is the card odd or even? ( )
33. Cold drink shops stipulate that after drinking soda, you can exchange three empty soda bottles for one bottle. Xiaoming's mother bought 19 bottles of soda. According to the regulations in the store, the last one can drink () bottles.
34. Divide a circular piece of paper with straight lines. Four straight lines can be divided into () at most.
35. A snail climbs15m bamboo pole, climbs 3m and slides 2m every day. It takes () days to climb this bamboo pole.
36. Four good friends Wen Wen, Fang Fang, Yuan Yuan and Zhuo Zhuo met. Every two people shake hands, they shake hands once.
37. A rope was cut five times and divided into () sections.
38. My brother sent his eight books to my sister, so my sister has as many books as my brother, and my brother has more books than his sister ().
39. There are 10 billiards with the same appearance and shape, one of which is a heavy and clever boy. If there is balance,
You can find the ball at least () times.
40. There are 45 students in Class 3 (1), 29 students join the math group, and 16 students join the language group. 1 1 person, both groups participated. Then, () people didn't participate in both groups.