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一、混合运算小学第五册(六年制)第二单元的混合运算,是小学数学教学先乘除后加减和脱括号运算的开始.它是在加、减、乘、除计算的基础上进行教学,是进一步学习四则混合运算的基础.教学这部分知识的关键是让学生掌握运算顺序,培养学生的计算能力.这部分内容的教学,可按如下步骤进行.首先在教学34页的例1、例2前,先让学生复习只含同级运算的两步计算题.如:(1)165-15+2,(2)130+21-3,(3)6÷2×3,(4)6×2÷3.让学生回答运算顺序,再口算出得数.随后教师出示尝试题:①165—15×2,②130+21÷3.让学生自学课本例1和例2.教师注意指导学生看例题中的箭头和旁注.通过尝试练习、学生讨论和教师总结,使学生掌握先乘除、后加减的运算顺序.在教学书上第36页的例3和例4时,教师可先让学生计算;11×4+2和100-95÷5,然后给它加括号,
First, the mixed operation of the fifth primary school (six years) The second unit of hybrid computing, primary school mathematics teaching first multiplication and division addition and subtraction and the beginning of the operation of the bracket. It is in addition, subtraction, multiplication, addition to the calculation based on Teaching, is to further study the basis of the four mixed computing.The key to teaching this part of the knowledge is to enable students to master the order of operations, to develop students' computing power.This part of the content of teaching, according to the following steps.First of all, in teaching 34 cases 1, Example 2, let the students review only two steps with the same level computing questions, such as: (1) 165-15 +2, (2) 130 +21-3, (3) 6 ÷ 2 × 3, (4) 6 × 2 ÷ 3. Let the students answer the order of operation, and then calculate the number of mouth and then show the teacher to try the questions: ① 165-15 × 2, ② 130 + 21 ÷ 3. Students self-study example 1 and Example 2. Teachers Attention to guide students to see the examples of the arrow and side note by teaching practice, student discussion and teacher summary, so that students master the first multiplication and division, the addition and subtraction of the order of operations in the teaching book on page 36 cases 3 and 4, Teachers can let students calculate; 11 × 4 + 2 and 100-95 ÷ 5, and then give it in brackets,