first kind
Title: One-step application problem for finding the score of a number.
Teaching goal: on the basis of understanding the significance of fractional multiplication, make students learn to analyze the quantitative relationship of multiplication application problems; With the help of line graph, we can correctly answer the practical question of finding the score of a number; Cultivate students' good habits of careful examination and careful calculation.
Emphasis and difficulty in teaching: to understand the arithmetic of "what is the fraction of a number" by multiplication; Find the quantity corresponding to the unit "1" correctly, and learn to draw line segments initially.
Teaching process:
(1) import
1, show the cards of oral calculation and ask the students to say the meaning of each formula.
12× = × = × = × =
10× = × = × =
2. Oral introduction
What is 20? How much is 6? What is the number of 120?
(B), the implementation of teaching
1, show me the example on page 17 1.
Students read the questions and find out the known conditions and problems to be solved;
On the basis of understanding the meaning of the problem, express the quantitative relationship with charts, such as:
? ㎡ ? ㎡
2500㎡
2500㎡
2. Instruct students to draw line drawings and write down on the blackboard:
2500㎡
? ㎡
Question: Which known field should we focus on? What does this line segment mean?
According to the condition that "China's per capita arable land area only accounts for the world's per capita arable land area", how many parts should this line segment be divided equally? How to express it? (Ask one student to perform on the blackboard, other students try to draw by themselves, and the teacher makes a patrol.) Compare the blackboard and correct the incorrect places.
1, the quantitative relationship in the analysis problem
Question: Think about it. What does the phrase "China's per capita arable land only accounts for the world's per capita arable land" mean? (The per capita arable land area in the world is "1", and the unit "1" is divided into five parts on average, and the per capita arable land area in China accounts for two parts. ) For the per capita arable land area of China, who is a fraction? According to the relationship between the above quantities, how should this question be formulated? According to what?
Blackboard: 2500× = 1000 (m2) or 2500 ÷ 5× 2 = 1000 (m2).
What does this formula mean? Divide 2500 into five parts on average, and then work out how many such parts there are. That is, how much is 2500? )
(3), consolidate the exercise
1, reading a book, means dividing the unit "1" () into () copies on average, with the number of pages read accounting for such () copies and the rest accounting for () copies.
2. Complete the "doing" on page 17 of the textbook. Note: A person's height is the length of a whale. Who is regarded as the unit "1" here, and who is divided into several shares on average? Can it be represented by a line segment diagram? Ask the height of this person, that is, what?
3. Complete questions 2 and 3 in Exercise 4.
(4), class summary
We are answering the question, "Given a number, what is its score?" When applying this kind of fractional multiplication problem, we should first find the quantity corresponding to the unit "1" in the problem, and then calculate it according to the meaning of fractional multiplication.