The significance of Wu Zhengxian ratio is recorded in class as follows:
Teaching content: make students understand the meaning of comparison, master the names of various parts of comparison, read and write the ratio correctly and find the ratio correctly. Guide students to strengthen the connection between knowledge, systematize knowledge and improve their ability to analyze and solve problems. Teaching emphasis: understand the meaning of ratio and the relationship between ratio and division and fraction.
Teaching difficulty: make clear the connection and difference between ratio and ratio. Teaching preparation: courseware, projection. Teaching process: creating situations and generating problems. Teacher: Students, do you know the name of the first manned spaceship in China? (Show the situation map)
Q: How to express the length-width relationship of the national flag with an expression? (Lead the students to say: How many times can you ask for the length? Or how long is the red flag? ) summary: the multiple relationship between length and width can be expressed by division.
Explore communication and solve problems:
The meaning of ratio: the ratio of two similar quantities, and compare the relationship between these two quantities. In addition to division, there is also a mathematical expression, namely "ratio". It can be said that the aspect ratio is 15 to 10, or the aspect ratio is 10 to 15.
No matter the aspect ratio or the aspect ratio, it is the ratio of two lengths, and the two quantities compared are of the same kind. Thinking: When two quantities form a ratio, who is better than who, who is in front and who is behind, can we exchange places? Why? (Group communication, report supplement, deeply understand the significance of comparison)
After entering the orbit, Shenzhou 5, with two different scales, made a circular motion at a height of 350 kilometers from the ground, circling the earth for 90 minutes on average, running about 42,252 kilometers. How to use the formula to express how many kilometers per minute the spacecraft flies on average after entering orbit? (Equation: 42252-90, based on the fact that speed can be expressed by distance-time)
For this relationship, we can also say that the ratio of the distance and time traveled by the spacecraft is 42,252 to 90, where 42,252 kilometers and 90 hours are two different quantities.
Q: What does the ratio of distance to time mean? (Students speak freely and understand that "distance is faster than time" is speed) The meaning of inductive ratio. What do you think is comparison through the above two examples? (Students try to say, the teacher concludes: The division of two numbers is also called the ratio of two numbers. ) than writing; Teaching materials for self-study reading: how to write? How to read?
What is the name of Bi's parts? How to find the ratio? How to express the proportion? What are the connections and differences between Bibi and Bibi? Group exchange report. Relationship between ratio, division, fraction and division
Q: What is the equivalent of the previous paragraph? What is the equivalent of the latter term? What is the proportion equivalent to? Can the last term of the ratio be zero? Why? Group exchange report. The relationship between ratio and score.
According to the relationship between fraction and division, what is the relationship between ratio and fraction? (Guide the students to answer: the former term of ratio is equivalent to numerator, the latter term is equivalent to denominator, and the ratio is equivalent to the value of fraction. )
Consolidate application and internalize promotion: complete the textbook "Do it"; Exercise 1 1, question 1 and 2. Review, Reflection and Improvement: What did you get from this lesson? After-school extension: what is the comparison in life? What does this mean? Blackboard design: the significance of comparison.