Teaching objectives:
1, connecting with real life, create an inquiry situation, so that students can initially grasp the quantitative relationship of the application problems of fractional multiplication and learn to apply the meaning of fractional multiplication to solve the one-step application problems of fractional multiplication.
2. Cultivate students' analytical ability and develop their thinking by observing, guessing, trying to practice and exchanging feedback.
3. Create an open, democratic and interesting space for independent inquiry, encourage students to question boldly and cultivate innovative ability.
4. By understanding the example 1 and comparing the per capita cultivated land area in China with that in the world, we know that the contradiction between population and land in China is increasingly prominent, so we should control population growth, protect cultivated land and care for the environment.
Teaching emphasis: Understand the relationship between the unit "1" in the question and the question.
Difficulties in teaching: Grasp the key of knowledge and correctly and flexibly judge the unit "1".
Teaching process:
First, review.
1, say the meaning of the following formula first, and then calculate the number orally.
12××
2. Column calculation.
How much is (1)20? (2) What is 6?
Students come to the conclusion that multiplication is used to find the fraction of a number.
Second, new funding.
1, teaching example 1: The per capita cultivated land area in the world is 2,500 square meters, and the per capita cultivated land area in China only accounts for the per capita cultivated land area in the world. What is the per capita arable land area in China?
(1) Guide students to grasp the key sentence "China's per capita cultivated land area only accounts for the world's per capita cultivated land area", understand the meaning of the problem with line graphs, and find a solution to the problem.
(2) Organize students to discuss how to understand this fractional sentence. (Through discussion, make the students understand that this sentence is to compare "China's per capita arable land area" with "the world's per capita arable land area", where "the world's per capita arable land area" refers to the unit "1". Knowing that the per capita arable land area in the world is 2,500 square meters, we can work out the per capita arable land area in China.
How much is 2500)
Per capita arable land area in China = per capita arable land area in the world.
(3) On the basis of analyzing the meaning of the questions, students make and calculate independently.
2500× 1000 (m2)
2, combined with the calculation results, let students talk about their own ideas, cultivate students' ability to analyze data. Through comparative calculation, it is found that the per capita cultivated land area in China is less than that in the world 1.500 square meters. Knowing that the contradiction between China's large population and small land is very prominent, and China's soil erosion is very serious now, it is necessary to educate students on protecting cultivated land, caring for the environment and family planning.
3. Consolidation exercise: "Do it", let students draw a line chart to express the meaning of the problem and talk about their own ideas. What is the basis? Then answer independently.
Third, practice.
1, the length of whale is 28 meters, and the height of human is 2/35 of the length of whale. How tall is this man?
Process requirements:
(1) Students think independently and explain in columns.
(2) (the result of peer communication thinking process)
(3) Report the solution process:
Relationship: human height = 2/35 of whale length.