Teaching process:
(1) import
1, say the meaning of the following formula, and then calculate the questions orally.
×2= ×3= × = × = 36× =
2. Name two quantities in the following questions and see who the unit "1" should be. Then add a known condition and a question to each question to make it a fractional multiplication application problem calculated step by step.
The number of cows is the number of cows, and the number of cows is equal to the number of cows.
The number of cows is equivalent to the number of cows' heads, and the number of cows' heads is equivalent to the number of cows.
Group completion, collective revision.
(B), the implementation of teaching
1. Blackboard: 30 bulls, the number of cows is equivalent to bulls, and the number of calves is equivalent to wooden cows. How many calves are there? Read the question carefully and find out the meaning of the question.
2. Instruct students to draw line drawings: How to express known conditions and problems with line drawings? To ask the number of calves, you need to know which quantity. (Number of cattle) What number does the number of cattle relate to? (Number of bulls) Draw a line segment first to indicate which number? (Number of bulls) What number does a line segment represent? How long is the picture (the number of cows)? According to what? How to draw a line segment representing the number of calves? Blackboard writing:
Bull: |||||||||||
30 heads
Cattle: ||
Calf:
? head
3. Analyze the quantitative relationship:
How many calves do you have? What do you want to ask first? How to find the number of cattle? How many steps are needed to solve this problem?
4. Column solution: According to the above analysis, how should this problem be solved? How to make a comprehensive solution? Blackboard writing:
30× × =
According to the comprehensive formula, let the students talk about what each step is seeking and which quantity is "1" in each step. At the same time, it is emphasized that decimal multiplication does not need to be calculated once like integer and decimal multiplication, but can be calculated once. When an integer multiplies a fraction, the denominator of the fraction should be used to approximate the fraction, and the fraction cannot be multiplied directly.
(3) Consolidate exercises
Complete questions 4, 5, 9 and 10 on page 18. Students should explain the meaning of each step and which quantity the unit "1" looks at in each step.
(4) Summary: The similarity between the two-step fractional multiplication application problem and the one-step fractional multiplication application problem is to find the score of a number, but the difference is that the fractional multiplication application problem needs to find the score of a number continuously. The key to solving the problem is to find out the unit of each step "1".