2. In the process of learning algorithms and solving practical problems, cultivate reasonable reasoning ability and mathematical application consciousness.
3. Get a successful experience in mathematics activities, and further enhance the interest in learning mathematics.
Teaching emphasis: a simple algorithm of multiplying the last three digits of the multiplier by 0 and one digit.
Teaching difficulties: 0 List the corresponding vertical forms correctly.
Teaching countermeasures: combining with specific questions, explain some rules and how to list vertical forms correctly. The multiplier has three digits, and the middle 0 is multiplied by one digit.
Teaching preparation: teaching wall chart.
Teaching process design:
First, review.
1、9×0 0×3 0×49×3 3×4×5×6×7×0
(1) Students do oral calculations.
(2) Tell me how you calculate so fast. Point out: multiply 0 by any number to get 0.
2. Use vertical calculation.
309×2 408×5
Students estimate the approximate figures first, and then calculate the figures vertically.
Second, new funding.
1. Presentation: Picture P83, 4× 120 column.
(1).
(2) Students' Speaking Method: You can calculate orally or vertically. Students are required to use vertical calculation.
(3) List the formulas, and the teacher will guide you to write simple methods and explain the algorithm.
2. Show: Give it a try, and the students will finish it in the book.
3. Collective explanation: It is pointed out that 9 and 7 in 700×9 are aligned.
4. How to calculate the multiplication with 0 at the end of the multiplier? Students talk about methods.
Third, consolidate
1. Show, think and do 1. Students do it and say it.
2. Think about doing 3. Note that there are two different algorithms for comparing multipliers: 0 in the middle and 0 at the end, but both of them are based on a number multiplied by 0 to get 0.
(1) Pay attention to comparison: When can I use a simple algorithm? When can't I?
(2) Why are there 1 zeros at the end of the multiplier and two zeros at the end of the number?
(3) blackboard title: multiplication with 0 at the end of multiplier.
3. Display:
2 10×3 120×2 400×9 5×90 5× 12 403×2 200×5 1 12×3 25×4 1300×3
(1) Ask students to find out what can be simplified and what can't.
(2) keep your promise.
(3) Judge:
A. There are 1 zeros at the end of the multiplier, and only 1 zeros at the end of the number. Why?
B. If there are 1 zeros at the end of the multiplier, add a zero at the end of the multiplier.
C, there is no 0 at the end of the multiplier and no 0 at the end of the number.
Students judge and then give examples to explain why it is wrong or right.
4, oral calculation, think about doing 4, what did you find? Ask the students to say that it is easier to multiply the first two digits by a number and then add a 0 at the end.
5. Think it over, and then do it when you are finished. 7. Do it yourself. After finishing, discuss in groups. What did you find? Communicate findings in class.
Fourth, after-class summary:
What did you learn in this class?
Verb (abbreviation for verb) assigns homework.
Think about doing questions 2, 5 and 6.
Blackboard design: Multiplication with 0 at the end of multiplier
4× 120=
Think: To find the total number of people is to find out what four 120 is. [