Claim the lost property.
Li Lei found RMB A near the flag-raising platform on campus, and asked the owner to come to the Young Pioneers Brigade to claim it.
Xiao young pioneers team headquarters
2002.3
The students were surprised at the way the teacher talked about lost and found in math class. By analyzing and discussing the meaning of monism,
Teacher: Can one yuan be 1 yuan? Student 1: One yuan can be 1 yuan, which means 1 yuan has been found.
Teacher: Can one yuan be 5 yuan money? Health 2: Yes! Said to change 5 yuan.
Teacher: How much can a dollar have? Health 3: It can also be 85 yuan, which means you found 85 yuan's money.
Teacher: How much can a dollar have? Health 4: It can also be 0.5 yuan, which means you got 50 cents. ……
Teacher: So can one yuan be 0 yuan? Health 5: Absolutely not. If it is 0 yuan, then this lost and found notice is a big joke to everyone!
Teacher: Why not just say how much you found and use one yuan instead? ……
Because it is easy for students to know concrete and definite objects, and the numbers represented by letters are uncertain and changeable, it is often difficult for students to understand when they start learning. The "lost and found notice" in this topic is a familiar activity for students, which stimulates their desire to learn new knowledge, and students can participate in the problem-solving process involuntarily. In discussion and communication, brainstorming enables students to learn new knowledge in a pleasant atmosphere and to understand and master what they have learned more firmly; On the other hand, it also improves interpersonal skills, enhances the awareness of mutual assistance and cooperation, receives a good ideological education, and also exercises students' insight into society.
2, using mathematical knowledge to solve practical problems
For example, after learning the calculation of rectangular and square areas and the calculation of combined graphics, I try my best to let students use what they have learned to solve practical problems in life. The teacher's home has a two-bedroom apartment, as shown in the picture. Can you help him calculate the living area of two rooms and one living room? To calculate the size of the area, which area should we measure first? Let the students calculate after giving some data; Next, I asked the students to go home and measure the actual living area of their home. In this practical calculation process, not only the interest is improved, but also the ability of practical measurement and calculation is cultivated, so that students can learn and use it in their lives.
For example, after learning the addition and subtraction within 100, the teaching situation of "buying a car" was created: the price of a mini-car was greatly reduced, and Kobayashi spent 100 yuan to buy several cars. How many cars did he buy? Which ones?
Through observation, thinking and discussion, with my encouragement and guidance, the students expressed the following in an orderly way:
(1) decompose 100 into the sum of two numbers: (2) decompose 100 into the sum of three numbers:
50+50= 100 40+60= 100 30+70= 10020+80= 100 60+20+20= 10050+20+30= 10040+40+20= 10030+30+40= 100
(3) decompose 100 yuan into the sum of four numbers (4) decompose 100 yuan into the sum of five numbers 40+20+20 = 100.
20+20+20+20+20= 100 30+30+20+20= 100
1. In order to investigate the math scores of 3500 junior high school graduates in a city, 20 test papers were selected, each with 30 copies. The total of this question is: (Math scores of 3500 junior high school graduates in a city) The single item is: (1 Math scores of graduates) The sample is: (Math scores of 600 graduates) The sample size is: (600) 2. In the triangle ABC, the angle C=90 degrees, and the lengths of AC and BC are the square of equation X respectively. 2. Let PE⊥BC be in E, PD⊥AC be in D, PF⊥AB be in f∫ Solve the square of equation X -7X+12=0: X1= 3x2 = 4 ∴ AC=3, BC.
Honghua shirt factory wants to produce a batch of shirts. It originally planned to produce 400 shirts a day and finish them in 60 days. The actual number of pieces produced per day is 65438+ 0.5 times of the original planned number of pieces produced per day. How many days did it actually take to complete the task of making these shirts?
To analyze and understand how many days it takes to complete the task of making these shirts, we must know the total number of these shirts and the actual number of them produced every day. Knowing that the original plan was to produce 400 pieces a day and complete them in 60 days, we can find out the total number of these shirts; Knowing that the number of pieces actually produced every day is 65438+ 0.5 times of the original planned number, we can find out the number of pieces actually produced every day.
The actual number of days to complete these shirt-making tasks is:
40060(400 1.5)
=24000600
=40 days
It can also be considered that the total number of shirts to be produced is certain, so the number of days required to complete the task of making these shirts is inversely proportional to the number of shirts produced every day. It can be concluded that the number of days to actually complete the task of making these shirts is 1.5 times, which is exactly 60 days, so it is concluded that the number of days actually needed to make these shirts is:
60 1.5=40 (days)
A: It actually took 40 days to complete the task of making these shirts.
Example 2: Dongfeng Machinery Factory originally planned to produce 240 parts per day, which was completed in 18 days. It was actually finished three days ahead of schedule. How many more parts are actually produced every day than originally planned?
Analysis and solutions require how many more parts are actually produced every day than originally planned. First, find out the number of parts actually produced every day, and then subtract the number of parts planned to be produced every day:
240 18( 18-3)-240
=4320 15-240
=288-240
=48 (pieces)
You can also think that the total number of parts actually completed and planned is the same. According to the meaning of inverse proportion, the number of parts produced every day is inversely proportional to the number of days required to complete the production of these parts. Therefore, the ratio of the number of days originally planned to complete the task to the number of days actually completed the task is 18: (18-3), that is, 6: 5, that is, the ratio of the number of parts actually produced every day to the number of parts originally planned to produce every day. Of course, the actual number of parts produced every day is 6/5 of the original planned number of parts produced every day. So find out the number of parts actually produced every day than originally planned:
=48 (pieces)
You can also think of it this way: the total number of parts produced is 240 18=4320 (pieces); This number is decomposed into prime factors, and then the decomposed prime factors are appropriately grouped to represent the product of the original planned daily production number and the number of completed days and the product of the actual daily production number and the actual number of completed days respectively.
4320=25×33×5
= (24× 35) (232) ... The quantity and completion of the original planned daily output.
Tiande products
= (25× 32 )× (35) ... Actual daily output and days of completion.
product
Then find out how much the actual daily output exceeds the original plan:
25×32-24×35
=288-240
=48 (pieces)
A: Actually, 48 more units are produced every day than originally planned.