What knowledge did you learn about division by oral arithmetic in unit 6 of Volume 1 of grade 4

What knowledge did you learn about division by oral arithmetic in unit 6 of Volume 1 of grade 4

Division by oral arithmetic is the first lesson in unit 2 of mathematics volume 5 of grade 3. It is based on students' mastery of table multiplication and multiplication of one digit by many digits. It lays a certain foundation of knowledge and thinking for learning division estimation and division by written arithmetic
First, prepare for necessary review. New knowledge is always based on old knowledge. In the second grade, students learned the knowledge of table multiplication and quotient by using multiplication formula. But after a summer break, many students have forgotten it. So I strengthened the review and inspection of table multiplication formula as soon as the semester started to prepare for learning this book, In the teaching design of this lesson, we review the significance of division by hands, such as: 6 ／ 2 is to divide 6 (), each of which is () and () respectively, and the composition of tens, hundreds and thousands, digit and counting unit knowledge, etc., which means to wake up students' cognitive consciousness and prepare for the transfer of new knowledge in this lesson
Second, let the students explore the algorithm independently and experience the formation process of knowledge. Learning is not a simple "tell", but a kind of learner's real "experience" and "accumulation". In teaching, I create learning and inquiry situation for students, guide students to make full use of existing knowledge and experience, through the way of pendulum, point, say, etc, In the process of exploration and communication, the students enjoy the joy of success and enhance their confidence in learning. In the teaching, the students are encouraged to use a variety of methods to solve the problem of 40 △ 2 in table tennis. The students say two methods: (1) don't look at "0" first, 4 △ 2 = 2, and then add "0", "2" becomes "20". I guide the students to realize that the 4 is not the 4 we usually know, but the 4 tens, so the division is 2 tens. We should add a "0" (2) multiplication and division after the 2, which is a good friend. If we want to () × 2 = 40, we can also calculate the result. Through the students' speeches, we can make the students express the calculation process as concise as possible, Gradually cultivate students' language expression ability. Give full play to students' consciousness of independent exploration, give play to students' subjectivity in the process of solving problems, and guide students to summarize and consolidate in time, so as to internalize knowledge

Oral division 90 △ 30 = 40 △ 10 = 120 △ 20 = 160 △ 40 = 149 △ 50 ≈ 180 △ 32 ≈ 353 △ 70 ≈ 720 ／ 87 ≈

90÷30=3， 40÷10=4， 120÷20=6， 160÷40=4， 149÷50≈3， 180÷32≈6， 353÷70≈5， 720÷87≈8．

What are the rules of binary addition and multiplication?

Binary multiplication and addition are realized by shifting binary numbers. The shift is equivalent to x 2. The computer calculates how many bits to shift according to the given addition and multiplication formulas